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<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
<title>TIME IN PIECE</title>
<subtitle>I MUST ASSEMBL THEM</subtitle>
<link href="https://wicherqaq.github.io/atom.xml" rel="self"/>
<link href="https://wicherqaq.github.io/"/>
<updated>2020-12-23T09:37:18.313Z</updated>
<id>https://wicherqaq.github.io/</id>
<author>
<name>wicherQAQ</name>
</author>
<generator uri="https://hexo.io/">Hexo</generator>
<entry>
<title>spring 配置 cache 缓存使用 Redis（基于注解）</title>
<link href="https://wicherqaq.github.io/2020/12/23/spring-%E9%85%8D%E7%BD%AE-cache-%E7%BC%93%E5%AD%98%E4%BD%BF%E7%94%A8-Redis%EF%BC%88%E5%9F%BA%E4%BA%8E%E6%B3%A8%E8%A7%A3%EF%BC%89/"/>
<id>https://wicherqaq.github.io/2020/12/23/spring-%E9%85%8D%E7%BD%AE-cache-%E7%BC%93%E5%AD%98%E4%BD%BF%E7%94%A8-Redis%EF%BC%88%E5%9F%BA%E4%BA%8E%E6%B3%A8%E8%A7%A3%EF%BC%89/</id>
<published>2020-12-23T09:32:57.000Z</published>
<updated>2020-12-23T09:37:18.313Z</updated>
<content type="html"><![CDATA[<h2 id="Spring-boot默认使用的是SimpleCacheConfiguration，即使用ConcurrentMapCacheManager来实现缓存。"><a href="#Spring-boot默认使用的是SimpleCacheConfiguration，即使用ConcurrentMapCacheManager来实现缓存。" class="headerlink" title="Spring boot默认使用的是SimpleCacheConfiguration，即使用ConcurrentMapCacheManager来实现缓存。"></a>Spring boot默认使用的是SimpleCacheConfiguration，即使用ConcurrentMapCacheManager来实现缓存。</h2><p>Spring cache是代码级的缓存，一般是使用一个ConcurrentMap，也就是说实际上还是是使用JVM的内存来缓存对象的，这势必会造成大量的内存消耗。但好处是显然的：使用方便。<br> Redis 作为一个缓存服务器，是内存级的缓存。它是使用单纯的内存来进行缓存。<br> 集群环境下，每台服务器的spring cache是不同步的，这样会出问题的，spring cache只适合单机环境。<br> Redis是设置单独的缓存服务器，所有集群服务器统一访问redis，不会出现缓存不同步的情况。</p><h3 id="CacheManager负责对缓存的增删改查-CacheManager的缓存的介质可配置ConcurrentMap-EhCache-Redis等，这里我用的是redis配置"><a href="#CacheManager负责对缓存的增删改查-CacheManager的缓存的介质可配置ConcurrentMap-EhCache-Redis等，这里我用的是redis配置" class="headerlink" title="CacheManager负责对缓存的增删改查, CacheManager的缓存的介质可配置ConcurrentMap/EhCache/Redis等，这里我用的是redis配置"></a>CacheManager负责对缓存的增删改查, CacheManager的缓存的介质可配置ConcurrentMap/EhCache/Redis等，这里我用的是redis配置</h3><p>Redis配置类</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br></pre></td><td class="code"><pre><span class="line">@Configuration</span><br><span class="line">public class RedisConfiguration {</span><br><span class="line"></span><br><span class="line"> @Bean</span><br><span class="line"> @ConfigurationProperties(prefix = "session.redis")</span><br><span class="line"> protected RedisConfigVo redisConfig() {</span><br><span class="line"> return new RedisConfigVo();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> /**</span><br><span class="line"> * 解决redis.clients.jedis.exceptions.JedisDataException: ERR unknown command ' CONFIG '</span><br><span class="line"> *</span><br><span class="line"> * @return</span><br><span class="line"> */</span><br><span class="line"> @Bean</span><br><span class="line"> public static ConfigureRedisAction configureRedisAction() {</span><br><span class="line"> return ConfigureRedisAction.NO_OP;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> /**</span><br><span class="line"> * 创建连接工厂</span><br><span class="line"> *</span><br><span class="line"> * @return</span><br><span class="line"> */</span><br><span class="line"> @Bean</span><br><span class="line"> public RedisConnectionFactory connectionFactory() {</span><br><span class="line"> RedisConfigVo configVo = redisConfig();</span><br><span class="line"> JedisConnectionFactory jedisConnectionFactory = new JedisConnectionFactory();</span><br><span class="line"> jedisConnectionFactory.setHostName(configVo.getHost());</span><br><span class="line"> jedisConnectionFactory.setPort(configVo.getPort());</span><br><span class="line"> jedisConnectionFactory.setTimeout(configVo.getTimeout());</span><br><span class="line"> if (configVo.getPassword() != null && !"".equals(configVo.getPassword())) {</span><br><span class="line"> jedisConnectionFactory.setPassword(configVo.getPassword());</span><br><span class="line"> }</span><br><span class="line"> jedisConnectionFactory.setDatabase(configVo.getDatabase());</span><br><span class="line"> jedisConnectionFactory.setPoolConfig(poolCofig(configVo));</span><br><span class="line"> jedisConnectionFactory.setUsePool(true);</span><br><span class="line"> // 初始化连接pool</span><br><span class="line"> jedisConnectionFactory.afterPropertiesSet();</span><br><span class="line"> return jedisConnectionFactory;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> /**</span><br><span class="line"> * 创建连接池配置</span><br><span class="line"> *</span><br><span class="line"> * @return</span><br><span class="line"> */</span><br><span class="line"> private static JedisPoolConfig poolCofig(RedisConfigVo configVo) {</span><br><span class="line"> JedisPoolConfig jedisPoolConfig = new JedisPoolConfig();</span><br><span class="line"> jedisPoolConfig.setMaxIdle(configVo.getMaxIdle() > 0 ? configVo.getMaxIdle() : GenericObjectPoolConfig.DEFAULT_MAX_IDLE);</span><br><span class="line"> jedisPoolConfig.setMinIdle(configVo.getMinIdle() > 0 ? configVo.getMinIdle() : GenericObjectPoolConfig.DEFAULT_MIN_IDLE);</span><br><span class="line"> jedisPoolConfig.setMaxTotal(configVo.getMaxTotal() > 0 ? configVo.getMaxTotal() : GenericObjectPoolConfig.DEFAULT_MAX_TOTAL);</span><br><span class="line"> jedisPoolConfig.setMaxWaitMillis(configVo.getMaxWaitMillis() > 0 ? configVo.getMaxWaitMillis() : GenericObjectPoolConfig.DEFAULT_MAX_WAIT_MILLIS);</span><br><span class="line"> jedisPoolConfig.setTestOnBorrow(configVo.isTestOnBorrow());</span><br><span class="line"> return jedisPoolConfig;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> @Bean</span><br><span class="line"> public CacheManager cacheManager(RedisTemplate redisTemplate) {</span><br><span class="line"></span><br><span class="line"> RedisCacheManager rcm = new RedisCacheManager(redisTemplate);</span><br><span class="line"> //seconds</span><br><span class="line"> rcm.setDefaultExpiration(5 * 60L);</span><br><span class="line"> return rcm;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>使用@Cacheable 注解<br> <img src="/2020/12/23/spring-%E9%85%8D%E7%BD%AE-cache-%E7%BC%93%E5%AD%98%E4%BD%BF%E7%94%A8-Redis%EF%BC%88%E5%9F%BA%E4%BA%8E%E6%B3%A8%E8%A7%A3%EF%BC%89/.._posts%5Cspring-%E9%85%8D%E7%BD%AE-cache-%E7%BC%93%E5%AD%98%E4%BD%BF%E7%94%A8-Redis%EF%BC%88%E5%9F%BA%E4%BA%8E%E6%B3%A8%E8%A7%A3%EF%BC%89%5C1.png" alt></p>]]></content>
<summary type="html"><h2 id="Spring-boot默认使用的是SimpleCacheConfiguration，即使用ConcurrentMapCacheManager来实现缓存。"><a href="#Spring-boot默认使用的是SimpleCacheConfiguration，即使</summary>
<category term="springboot" scheme="https://wicherqaq.github.io/tags/springboot/"/>
</entry>
<entry>
<title>git同时配置gitee和github</title>
<link href="https://wicherqaq.github.io/2020/12/11/git%E5%90%8C%E6%97%B6%E9%85%8D%E7%BD%AEgitee%E5%92%8Cgithub/"/>
<id>https://wicherqaq.github.io/2020/12/11/git%E5%90%8C%E6%97%B6%E9%85%8D%E7%BD%AEgitee%E5%92%8Cgithub/</id>
<published>2020-12-11T08:21:08.000Z</published>
<updated>2021-07-25T02:27:45.983Z</updated>
<content type="html"><![CDATA[<h4 id="ssh文件本地环境配置"><a href="#ssh文件本地环境配置" class="headerlink" title="ssh文件本地环境配置"></a>ssh文件本地环境配置</h4><ul><li><p>在自己系统中找到.ssh文件夹,将此目录下的文件全部删除</p><ul><li><p>方法一： 在GUI模式下手动寻找 （window系统在 “C:\Users\账号名.ssh ” ）<br><img src="https://img-blog.csdnimg.cn/2019071711052845.png" alt="在这里插入图片描述"></p></li><li><p>方法二： 鼠标右键打开 Git Bash，在弹出的窗口中输入</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">cd ~/.ssh # 进入.ssh文件夹</span><br></pre></td></tr></table></figure></li></ul></li><li><p>生成ssh配置文件</p><ul><li><p>在 .ssh 文件夹下鼠标右键打开 Git Base Here</p></li><li><p>输入命令：</p><figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">ssh-keygen -t rsa -C "xxxxx@xxxxx.com" # 填写自己Github / Gitee的邮箱</span><br></pre></td></tr></table></figure></li><li><p>上述命令的执行次数由你要绑定几个代码仓库有关（eg: 要同时绑定Github和Gitee，则上述命令需执行两次），执行的时候可以自己指定生成文件的文件名（默认是id_rsa），然后填写密码（可以为空）：</p><figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">Generating public/private rsa key pair.</span><br><span class="line">Enter file in which to save the key (C:/Users/jiaha/.ssh): github_rsa</span><br></pre></td></tr></table></figure></li></ul></li><li><p>创建config文件，写入一些相应配置</p><p><code>touch config</code></p><figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#</span><span class="bash"> gitee</span></span><br><span class="line">Host gitee.com</span><br><span class="line">HostName gitee.com</span><br><span class="line">PreferredAuthentications publickey</span><br><span class="line">IdentityFile ~/.ssh/id_rsa.gitee</span><br><span class="line"></span><br><span class="line"><span class="meta">#</span><span class="bash"> github</span></span><br><span class="line">Host github.com</span><br><span class="line">HostName github.com</span><br><span class="line">PreferredAuthentications publickey</span><br><span class="line">IdentityFile ~/.ssh/id_rsa.github</span><br><span class="line">1234567891011</span><br></pre></td></tr></table></figure></li></ul><h4 id="在Github、Gitee上配置SSH-keys（以Github为例）"><a href="#在Github、Gitee上配置SSH-keys（以Github为例）" class="headerlink" title="在Github、Gitee上配置SSH keys（以Github为例）"></a>在Github、Gitee上配置SSH keys（以Github为例）</h4><ul><li>登录自己的Github / Gitee 网站，点击网站右上角自己的头像， 点击 Settings 选项，打开如下窗口，点击”New SSH key”。<br><img src="https://img-blog.csdnimg.cn/20190717134149744.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjIzMDU1MA==,size_16,color_FFFFFF,t_70" alt="在这里插入图片描述"></li><li>“文本框1”中可以自己填写一个自定义标识（可以随便填写），“文本框2”中将之前在本地生成的**_rsa.pub文件中的内容复制粘贴到这里即可。然后点击“Add SSH key”。<br><img src="https://img-blog.csdnimg.cn/201907171344244.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjIzMDU1MA==,size_16,color_FFFFFF,t_70" alt="在这里插入图片描述"></li></ul><h4 id="测试是否成功"><a href="#测试是否成功" class="headerlink" title="测试是否成功"></a>测试是否成功</h4><ul><li><p>打开 git 的控制窗口，输入如下命令：</p><figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#</span><span class="bash"> 测试连接 Github </span></span><br><span class="line">ssh -T git@github.com</span><br><span class="line"><span class="meta">#</span><span class="bash"> 测试连接 Gitee </span></span><br><span class="line">ssh -T git@gitee.com</span><br></pre></td></tr></table></figure></li><li><p>如果出现如下结果，则说明你已经配置成功了。<br><img src="https://img-blog.csdnimg.cn/20190717135314964.png" alt="在这里插入图片描述"></p></li></ul>]]></content>
<summary type="html"><h4 id="ssh文件本地环境配置"><a href="#ssh文件本地环境配置" class="headerlink" title="ssh文件本地环境配置"></a>ssh文件本地环境配置</h4><ul>
<li><p>在自己系统中找到.ssh文件夹,将此目录下的文件全</summary>
<category term="git" scheme="https://wicherqaq.github.io/categories/git/"/>
</entry>
<entry>
<title>DockerFile命令</title>
<link href="https://wicherqaq.github.io/2020/12/07/DockerFile%E5%91%BD%E4%BB%A4/"/>
<id>https://wicherqaq.github.io/2020/12/07/DockerFile%E5%91%BD%E4%BB%A4/</id>
<published>2020-12-07T02:30:13.000Z</published>
<updated>2020-12-07T02:37:15.835Z</updated>
<content type="html"><![CDATA[<h4 id="FROM命令"><a href="#FROM命令" class="headerlink" title="FROM命令"></a>FROM命令</h4><p>功能为指定基础镜像，并且必须是第一条指令。</p><p>如果不以任何镜像为基础，那么写法为：FROM scratch。</p><p>同时意味着接下来所写的指令将作为镜像的第一层开始</p><blockquote><p> 语法：</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">FROM <image></span><br><span class="line">FROM <image>:<tag></span><br><span class="line">FROM <image>:<digest> </span><br></pre></td></tr></table></figure><p>三种写法，其中<tag>和<digest> 是可选项，如果没有选择，那么默认值为latest</digest></tag></p></blockquote><h4 id="RUN命令"><a href="#RUN命令" class="headerlink" title="RUN命令"></a>RUN命令</h4><p>功能为运行指定的命令</p><p>RUN命令有两种格式</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">1. RUN <command></span><br><span class="line">2. RUN ["executable", "param1", "param2"]</span><br></pre></td></tr></table></figure><p>第一种后边直接跟shell命令</p><ul><li>在linux操作系统上默认 /bin/sh -c</li><li>在windows操作系统上默认 cmd /S /C</li></ul><p>第二种是类似于函数调用。</p><p>可将executable理解成为可执行文件，后面就是两个参数。</p><p>两种写法比对：</p><ul><li>```<br>RUN /bin/bash -c ‘source $HOME/.bashrc; echo $HOME<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">-</span><br></pre></td></tr></table></figure>RUN [“/bin/bash”, “-c”, “echo hello”]<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">注意：多行命令不要写多个RUN，原因是Dockerfile中每一个指令都会建立一层.</span><br><span class="line"></span><br><span class="line">多少个RUN就构建了多少层镜像，会造成镜像的臃肿、多层，不仅仅增加了构件部署的时间，还容易出错。</span><br><span class="line"></span><br><span class="line">RUN书写时的换行符是\</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line">#### CMD命令</span><br><span class="line"></span><br><span class="line">功能为容器启动时要运行的命令</span><br><span class="line"></span><br><span class="line">语法有三种写法</span><br></pre></td></tr></table></figure></li></ul><ol><li>CMD [“executable”,”param1”,”param2”]</li><li>CMD [“param1”,”param2”]</li><li>CMD command param1 param2<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">第三种比较好理解了，就时shell这种执行方式和写法</span><br><span class="line"></span><br><span class="line">第一种和第二种其实都是可执行文件加上参数的形式</span><br><span class="line"></span><br><span class="line">举例说明两种写法：</span><br><span class="line"></span><br><span class="line">-</span><br></pre></td></tr></table></figure>CMD [ “sh”, “-c”, “echo $HOME” <figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">-</span><br></pre></td></tr></table></figure>CMD [ “echo”, “$HOME” ]<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">补充细节：这里边包括参数的一定要用双引号，就是",不能是单引号。千万不能写成单引号。</span><br><span class="line"></span><br><span class="line">原因是参数传递后，docker解析的是一个JSON array</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line">##### RUN & CMD</span><br><span class="line"></span><br><span class="line">不要把RUN和CMD搞混了。</span><br><span class="line"></span><br><span class="line">RUN是构件容器时就运行的命令以及提交运行结果</span><br><span class="line"></span><br><span class="line">CMD是容器启动时执行的命令，在构件时并不运行，构件时紧紧指定了这个命令到底是个什么样子</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line">#### LABEL命令</span><br><span class="line"></span><br><span class="line">功能是为镜像指定标签</span><br><span class="line"></span><br><span class="line">语法：</span><br></pre></td></tr></table></figure>LABEL <key>=<value> <key>=<value> <key>=<value> …<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">一个Dockerfile种可以有多个LABEL，如下：</span><br></pre></td></tr></table></figure>LABEL “com.example.vendor”=”ACME Incorporated”<br>LABEL com.example.label-with-value=”foo”<br>LABEL version=”1.0”<br>LABEL description=”This text illustrates <br>that label-values can span multiple lines.”<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"> 但是并不建议这样写，最好就写成一行，如太长需要换行的话则使用\符号</span><br><span class="line"></span><br><span class="line">如下：</span><br></pre></td></tr></table></figure>LABEL multi.label1=”value1” <br>multi.label2=”value2” <br>other=”value3”<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">说明：LABEL会继承基础镜像种的LABEL，如遇到key相同，则值覆盖</span><br><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">#### MAINTAINER命令</span><br><span class="line"></span><br><span class="line">指定作者</span><br><span class="line"></span><br><span class="line">语法：</span><br></pre></td></tr></table></figure>MAINTAINER <name><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">#### EXPOSE命令</span><br><span class="line"></span><br><span class="line">功能为暴漏容器运行时的监听端口给外部</span><br><span class="line"></span><br><span class="line">但是EXPOSE并不会使容器访问主机的端口</span><br><span class="line"></span><br><span class="line">如果想使得容器与主机的端口有映射关系，必须在容器启动的时候加上 -P参数</span><br><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">#### ENV命令</span><br><span class="line"></span><br><span class="line">功能为设置环境变量</span><br><span class="line"></span><br><span class="line">语法有两种</span><br></pre></td></tr></table></figure></name></value></key></value></key></value></key></li><li>ENV <key> <value></value></key></li><li>ENV <key>=<value> …<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">两者的区别就是第一种是一次设置一个，第二种是一次设置多个</span><br><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">#### ADD命令</span><br><span class="line"></span><br><span class="line"> 一个复制命令，把文件复制到景象中。</span><br><span class="line"></span><br><span class="line">如果把虚拟机与容器想象成两台linux服务器的话，那么这个命令就类似于scp，只是scp需要加用户名和密码的权限验证，而ADD不用。 </span><br><span class="line"></span><br><span class="line">语法如下：</span><br></pre></td></tr></table></figure></value></key></li><li>ADD <src>… <dest></dest></src></li><li>ADD [“<src>“,… “<dest>“] <figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"><dest>路径的填写可以是容器内的绝对路径，也可以是相对于工作目录的相对路径</span><br><span class="line"></span><br><span class="line"><src>可以是一个本地文件或者是一个本地压缩文件，还可以是一个url</span><br><span class="line"></span><br><span class="line">如果把<src>写成一个url，那么ADD就类似于wget命令</span><br><span class="line"></span><br><span class="line">如以下写法都是可以的：</span><br><span class="line"></span><br><span class="line">-</span><br></pre></td></tr></table></figure>ADD test relativeDir/ <figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">-</span><br></pre></td></tr></table></figure>ADD test /relativeDir<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">-</span><br></pre></td></tr></table></figure>ADD <a href="http://example.com/foobar" target="_blank" rel="noopener">http://example.com/foobar</a> /<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">尽量不要把<scr>写成一个文件夹，如果<src>是一个文件夹了，复制整个目录的内容,包括文件系统元数据</span><br><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">#### COPY命令</span><br><span class="line"></span><br><span class="line">看这个名字就知道，又是一个复制命令</span><br><span class="line"></span><br><span class="line">语法如下：</span><br></pre></td></tr></table></figure></dest></src></li><li>COPY <src>… <dest></dest></src></li><li>COPY [“<src>“,… “<dest>“]<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">与ADD的区别</span><br><span class="line"></span><br><span class="line">COPY的<src>只能是本地文件，其他用法一致</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line">#### ENTRYPOINT命令</span><br><span class="line"></span><br><span class="line">功能是启动时的默认命令</span><br><span class="line"></span><br><span class="line">语法如下：</span><br></pre></td></tr></table></figure></dest></src></li><li>ENTRYPOINT [“executable”, “param1”, “param2”]</li><li>ENTRYPOINT command param1 param2<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">如果从上到下看到这里的话，那么你应该对这两种语法很熟悉啦。</span><br><span class="line"></span><br><span class="line">第二种就是写shell</span><br><span class="line"></span><br><span class="line">第一种就是可执行文件加参数</span><br><span class="line"></span><br><span class="line">与CMD比较说明（这俩命令太像了，而且还可以配合使用）：</span><br><span class="line"></span><br><span class="line">1. 相同点：</span><br><span class="line"></span><br><span class="line">- 只能写一条，如果写了多条，那么只有最后一条生效</span><br><span class="line">- 容器启动时才运行，运行时机相同</span><br><span class="line"></span><br><span class="line">2. 不同点：</span><br><span class="line"></span><br><span class="line">- ENTRYPOINT不会被运行的command覆盖，而CMD则会被覆盖</span><br><span class="line">- 如果我们在Dockerfile种同时写了ENTRYPOINT和CMD，并且CMD指令不是一个完整的可执行命令，那么CMD指定的内容将会作为ENTRYPOINT的参数</span><br><span class="line"></span><br><span class="line">如下：</span><br></pre></td></tr></table></figure>FROM ubuntu<br>ENTRYPOINT [“top”, “-b”]<br>CMD [“-c”]<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">- 如果我们在Dockerfile种同时写了ENTRYPOINT和CMD，并且CMD是一个完整的指令，那么它们两个会互相覆盖，谁在最后谁生效</span><br><span class="line"></span><br><span class="line">如下：</span><br></pre></td></tr></table></figure>FROM ubuntu<br>ENTRYPOINT [“top”, “-b”]<br>CMD ls -al<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">那么将执行ls -al ,top -b不会执行。</span><br><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">Docker官方使用一张表格来展示了ENTRYPOINT 和CMD不同组合的执行情况</span><br><span class="line"></span><br><span class="line">（下方表格来自docker官网）</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">#### VOLUME命令</span><br><span class="line"></span><br><span class="line">可实现挂载功能，可以将内地文件夹或者其他容器种得文件夹挂在到这个容器种</span><br><span class="line"></span><br><span class="line">语法为：</span><br></pre></td></tr></table></figure>VOLUME [“/data”]<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">说明：</span><br><span class="line"></span><br><span class="line"> ["/data"]可以是一个JsonArray ，也可以是多个值。所以如下几种写法都是正确的</span><br></pre></td></tr></table></figure>VOLUME [“/var/log/“]<br>VOLUME /var/log<br>VOLUME /var/log /var/db<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">一般的使用场景为需要持久化存储数据时</span><br><span class="line"></span><br><span class="line">容器使用的是AUFS，这种文件系统不能持久化数据，当容器关闭后，所有的更改都会丢失。</span><br><span class="line"></span><br><span class="line">所以当数据需要持久化时用这个命令。</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line">#### USER命令</span><br><span class="line"></span><br><span class="line">设置启动容器的用户，可以是用户名或UID，所以，只有下面的两种写法是正确的</span><br><span class="line"></span><br><span class="line">-</span><br></pre></td></tr></table></figure>USER daemo<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">-</span><br></pre></td></tr></table></figure>USER UID<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">注意：如果设置了容器以daemon用户去运行，那么RUN, CMD 和 ENTRYPOINT 都会以这个用户去运行</span><br><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">#### WORKDIR命令</span><br><span class="line"></span><br><span class="line">设置工作目录，对RUN,CMD,ENTRYPOINT,COPY,ADD生效。如果不存在则会创建，也可以设置多次。</span><br><span class="line"></span><br><span class="line">语法：</span><br></pre></td></tr></table></figure>WORKDIR /path/to/workdir<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">如：</span><br></pre></td></tr></table></figure>WORKDIR /a<br>WORKDIR b<br>WORKDIR c<br>RUN pwd<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">pwd执行的结果是/a/b/c</span><br><span class="line"></span><br><span class="line">WORKDIR也可以解析环境变量</span><br><span class="line"></span><br><span class="line">如：</span><br></pre></td></tr></table></figure>ENV DIRPATH /path<br>WORKDIR $DIRPATH/$DIRNAME<br>RUN pwd<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">pwd的执行结果是/path/$DIRNAME</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line">#### ARG命令</span><br><span class="line"></span><br><span class="line">语法：</span><br></pre></td></tr></table></figure>ARG <name>[=<default value>]<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">设置变量命令，ARG命令定义了一个变量，在docker build创建镜像的时候，使用 --build-arg <varname>=<value>来指定参数</span><br><span class="line"></span><br><span class="line">如果用户在build镜像时指定了一个参数没有定义在Dockerfile种，那么将有一个Warning</span><br><span class="line"></span><br><span class="line">提示如下：</span><br></pre></td></tr></table></figure>[Warning] One or more build-args [foo] were not consumed.<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">我们可以定义一个或多个参数，如下：</span><br></pre></td></tr></table></figure>FROM busybox<br>ARG user1<br>ARG buildno<br>…<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">也可以给参数一个默认值：</span><br></pre></td></tr></table></figure>FROM busybox<br>ARG user1=someuser<br>ARG buildno=1<br>…<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">如果我们给了ARG定义的参数默认值，那么当build镜像时没有指定参数值，将会使用这个默认值</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line">#### ONBUILD命令</span><br><span class="line"></span><br><span class="line">语法：</span><br></pre></td></tr></table></figure>ONBUILD [INSTRUCTION]<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">这个命令只对当前镜像的子镜像生效。</span><br><span class="line"></span><br><span class="line">比如当前镜像为A，在Dockerfile种添加：</span><br></pre></td></tr></table></figure>ONBUILD RUN ls -al<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">这个 ls -al 命令不会在A镜像构建或启动的时候执行</span><br><span class="line"></span><br><span class="line">此时有一个镜像B是基于A镜像构建的，那么这个ls -al 命令会在B镜像构建的时候被执行。</span><br><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">#### STOPSIGNAL命令</span><br><span class="line"></span><br><span class="line">*STOPSIGNAL命令是的作用是当容器推出时给系统发送什么样的指令*</span><br><span class="line"></span><br><span class="line">语法：</span><br></pre></td></tr></table></figure>STOPSIGNAL signal<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line">#### HEALTHCHECK命令</span><br><span class="line"></span><br><span class="line">*容器健康状况检查命令*</span><br><span class="line"></span><br><span class="line">语法有两种：</span><br></pre></td></tr></table></figure></default></name></li><li>HEALTHCHECK [OPTIONS] CMD command</li><li>HEALTHCHECK NONE<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">第一个的功能是在容器内部运行一个命令来检查容器的健康状况</span><br><span class="line"></span><br><span class="line">第二个的功能是在基础镜像中取消健康检查命令</span><br><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">[OPTIONS]的选项支持以下三中选项：</span><br><span class="line"></span><br><span class="line"> ***--interval=DURATION 两次检查默认的时间间隔为30秒***</span><br><span class="line"></span><br><span class="line"> ***--timeout=DURATION 健康检查命令运行超时时长，默认30秒***</span><br><span class="line"></span><br><span class="line"> ***--retries=N 当连续失败指定次数后，则容器被认为是不健康的，状态为unhealthy，默认次数是3***</span><br><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">注意：</span><br><span class="line"></span><br><span class="line">HEALTHCHECK命令只能出现一次，如果出现了多次，只有最后一个生效。</span><br><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">CMD后边的命令的返回值决定了本次健康检查是否成功，具体的返回值如下：</span><br><span class="line"></span><br><span class="line">***0: success - 表示容器是健康的***</span><br><span class="line"></span><br><span class="line">***1: unhealthy - 表示容器已经不能工作了***</span><br><span class="line"></span><br><span class="line">***2: reserved - 保留值***</span><br><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">例子：</span><br></pre></td></tr></table></figure>HEALTHCHECK –interval=5m –timeout=3s <br>CMD curl -f <a href="http://localhost/" target="_blank" rel="noopener">http://localhost/</a> || exit 1<pre><code></code></pre></li></ol><p>健康检查命令是：curl -f <a href="http://localhost/" target="_blank" rel="noopener">http://localhost/</a> || exit 1</p><p>两次检查的间隔时间是5秒</p><p>命令超时时间为3秒</p>]]></content>
<summary type="html"><h4 id="FROM命令"><a href="#FROM命令" class="headerlink" title="FROM命令"></a>FROM命令</h4><p>功能为指定基础镜像，并且必须是第一条指令。</p>
<p>如果不以任何镜像为基础，那么写法为：FROM sc</summary>
<category term="Docker" scheme="https://wicherqaq.github.io/tags/Docker/"/>
</entry>
<entry>
<title>LeetCode-283-移动0</title>
<link href="https://wicherqaq.github.io/2020/10/25/LeetCode-283-%E7%A7%BB%E5%8A%A80/"/>
<id>https://wicherqaq.github.io/2020/10/25/LeetCode-283-%E7%A7%BB%E5%8A%A80/</id>
<published>2020-10-25T02:27:53.000Z</published>
<updated>2020-10-25T02:29:34.042Z</updated>
<content type="html"><![CDATA[<p>给定一个数组 nums，编写一个函数将所有 0 移动到数组的末尾，同时保持非零元素的相对顺序。</p><p>示例:</p><p>输入: [0,1,0,3,12]<br>输出: [1,3,12,0,0]<br>说明:</p><p>必须在原数组上操作，不能拷贝额外的数组。<br>尽量减少操作次数。</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">class Solution(object):</span><br><span class="line"> def moveZeroes(self, nums):</span><br><span class="line"> """</span><br><span class="line"> :type nums: List[int]</span><br><span class="line"> :rtype: None Do not return anything, modify nums in-place instead.</span><br><span class="line"> """</span><br><span class="line"> # 0的个数</span><br><span class="line"> size = len(nums)</span><br><span class="line"> index = 0</span><br><span class="line"></span><br><span class="line"> for num in nums:</span><br><span class="line"> if num is not 0:</span><br><span class="line"> nums[index] = num</span><br><span class="line"> index+=1</span><br><span class="line"> </span><br><span class="line"> for i in range(size-index):</span><br><span class="line"> nums[index] = 0</span><br><span class="line"> index+=1</span><br></pre></td></tr></table></figure><h4 id="空间最优，操作局部优化（双指针）"><a href="#空间最优，操作局部优化（双指针）" class="headerlink" title="空间最优，操作局部优化（双指针）"></a>空间最优，操作局部优化（双指针）</h4><p>这种方法与上面的工作方式相同，即先满足一个需求，然后满足另一个需求。它以一种巧妙的方式做到了这一点。上述问题也可以用另一种方式描述，“将所有非 0 元素置于数组前面，保持它们的相对顺序相同”。<br>这是双指针的方法。由变量 “cur” 表示的快速指针负责处理新元素。如果新找到的元素不是 0，我们就在最后找到的非 0 元素之后记录它。最后找到的非 0 元素的位置由慢指针 “lastnonzerofoundat” 变量表示。当我们不断发现新的非 0 元素时，我们只是在 “lastnonzerofoundat+1” 第个索引处覆盖它们。此覆盖不会导致任何数据丢失，因为我们已经处理了其中的内容（如果它是非 0 的，则它现在已经写入了相应的索引，或者如果它是 0，则稍后将进行处理）。<br>在 “cur” 索引到达数组的末尾之后，我们现在知道所有非 0 元素都已按原始顺序移动到数组的开头。现在是时候满足其他要求了，“将所有 0 移动到末尾”。我们现在只需要在 “lastnonzerofoundat” 索引之后用 0 填充所有索引。</p><h4 id="复杂度分析"><a href="#复杂度分析" class="headerlink" title="复杂度分析"></a>复杂度分析</h4><p>时间复杂度：O(n)O(n)。但是，操作仍然是局部优化的。代码执行的总操作（数组写入）为 nn（元素总数）。<br>空间复杂度：O(1)O(1)，只使用常量空间。</p>]]></content>
<summary type="html"><p>给定一个数组 nums，编写一个函数将所有 0 移动到数组的末尾，同时保持非零元素的相对顺序。</p>
<p>示例:</p>
<p>输入: [0,1,0,3,12]<br>输出: [1,3,12,0,0]<br>说明:</p>
<p>必须在原数组上操作，不能拷贝额外的数组。</summary>
<category term="LeetCode" scheme="https://wicherqaq.github.io/categories/LeetCode/"/>
</entry>
<entry>
<title>windows安装rabbitmq</title>
<link href="https://wicherqaq.github.io/2020/10/21/windows%E5%AE%89%E8%A3%85rabbitmq/"/>
<id>https://wicherqaq.github.io/2020/10/21/windows%E5%AE%89%E8%A3%85rabbitmq/</id>
<published>2020-10-21T02:49:39.000Z</published>
<updated>2020-10-21T02:54:40.505Z</updated>
<content type="html"><![CDATA[<h1 id="Windows安装RabbitMQ"><a href="#Windows安装RabbitMQ" class="headerlink" title="Windows安装RabbitMQ"></a>Windows安装RabbitMQ</h1><h4 id="第一步：下载并安装erlang"><a href="#第一步：下载并安装erlang" class="headerlink" title="第一步：下载并安装erlang"></a>第一步：下载并安装erlang</h4><ul><li><ul><li>原因：RabbitMQ服务端代码是使用并发式语言Erlang编写的，安装Rabbit MQ的前提是安装Erlang。</li><li>下载地址：<a href="http://www.erlang.org/downloads" target="_blank" rel="noopener">http://www.erlang.org/downloads</a></li></ul></li></ul><p><img src="https://img2018.cnblogs.com/blog/773413/201910/773413-20191025144318759-1430833390.png" alt></p><p><img src="https://img2018.cnblogs.com/blog/773413/201910/773413-20191025144400115-2136772609.png" alt></p><ul><li>安装后要配置一下系统的环境变量。</li></ul><p>此电脑–>鼠标右键“属性”–>高级系统设置–>环境变量–>“新建”系统环境变量</p><p><img src="https://img-blog.csdn.net/20180208133656531?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvd2VpeGluXzM5NzM1OTIz/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70" alt></p><p>变量名：ERLANG_HOME</p><p>变量值就是刚才erlang的安装地址，点击确定。</p><p>然后双击系统变量path</p><p><img src="https://img-blog.csdn.net/20180208133941480?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvd2VpeGluXzM5NzM1OTIz/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70" alt="img"></p><p>点击“新建”，将%ERLANG_HOME%\bin加入到path中。</p><p><img src="https://img-blog.csdn.net/20180208134038141?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvd2VpeGluXzM5NzM1OTIz/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70" alt="img"></p><ul><li><p>最后windows键+R键，输入cmd，再输入erl，看到版本号就说明erlang安装成功了。</p></li><li></li></ul><h4 id="第二步：下载并安装RabbitMQ"><a href="#第二步：下载并安装RabbitMQ" class="headerlink" title="第二步：下载并安装RabbitMQ"></a>第二步：下载并安装RabbitMQ</h4><ul><li>下载地址：<a href="http://www.rabbitmq.com/download.html" target="_blank" rel="noopener">http://www.rabbitmq.com/download.html</a></li></ul><p><img src="https://img-blog.csdn.net/20180208140346384?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvd2VpeGluXzM5NzM1OTIz/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70" alt="img"></p><ul><li>双击下载后的.exe文件，安装过程与erlang的安装过程相同。</li><li>RabbitMQ安装好后接下来安装RabbitMQ-Plugins。打开命令行cd，输入RabbitMQ的sbin目录。</li></ul><p>我的目录是：D:\Program Files\RabbitMQ Server\rabbitmq_server-3.7.3\sbin</p><p>然后在后面输入rabbitmq-plugins enable rabbitmq_management命令进行安装</p><p><img src="https://img-blog.csdn.net/20180208141846581?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvd2VpeGluXzM5NzM1OTIz/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70" alt="img"></p><p>打开命令行命令行,进入RabbitMQ的安装目录: sbin</p><p>,输入 rabbitmqctl status , 如果出现以下的图，说明安装是成功的，并且说明现在RabbitMQ Server已经启动了,运行正常。</p><p><a href="http://jingyan.baidu.com/album/a17d5285173ce68098c8f2e5.html?picindex=11" target="_blank" rel="noopener"><img src="https://imgsa.baidu.com/exp/w=500/sign=f02f000de2dde711e7d243f697efcef4/b03533fa828ba61e8d9e78274634970a304e5941.jpg" alt="RabbitMQ在windows下的安装"></a></p><p>打开sbin目录，双击rabbitmq-server.bat</p><p><img src="https://img-blog.csdn.net/2018020814402581?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvd2VpeGluXzM5NzM1OTIz/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70" alt="img"></p><p>等几秒钟看到这个界面后，访问<a href="http://localhost:15672" target="_blank" rel="noopener">http://localhost:15672</a></p><p><img src="https://img-blog.csdn.net/20180208142631460?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvd2VpeGluXzM5NzM1OTIz/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70" alt="img"></p><p>然后可以看到如下界面</p><p><img src="https://img-blog.csdn.net/20180208144226627?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvd2VpeGluXzM5NzM1OTIz/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70" alt="img"></p><p>默认用户名和密码都是guest</p><p>登陆即可。</p>]]></content>
<summary type="html"><h1 id="Windows安装RabbitMQ"><a href="#Windows安装RabbitMQ" class="headerlink" title="Windows安装RabbitMQ"></a>Windows安装RabbitMQ</h1><h4 id="第一步：下</summary>
</entry>
<entry>
<title>python的切片操作</title>
<link href="https://wicherqaq.github.io/2020/10/07/python%E7%9A%84%E5%88%87%E7%89%87%E6%93%8D%E4%BD%9C/"/>
<id>https://wicherqaq.github.io/2020/10/07/python%E7%9A%84%E5%88%87%E7%89%87%E6%93%8D%E4%BD%9C/</id>
<published>2020-10-07T01:58:13.000Z</published>
<updated>2021-07-25T02:27:08.980Z</updated>
<content type="html"><![CDATA[<h4 id="写在前面："><a href="#写在前面：" class="headerlink" title="写在前面："></a>写在前面：</h4><p>利用python解决问题的过程中，经常会遇到从某个对象中抽取部分值的情况。“切片”操作正是专门用于实现这一目标的有力武器。理论上，只要条件表达式得当，可以通过单次或多次切片操作实现任意目标值切取。切片操作的基本语法比较简单，但如果不彻底搞清楚内在逻辑，也极容易产生错误，而且这种错误有时隐蔽得较深，难以察觉。本文通过详细例子总结归纳了切片操作的各种情形，下文均以list类型作为实验对象，其结论可推广至其他可切片对象。</p><h4 id="一、-Python可切片对象的索引方式"><a href="#一、-Python可切片对象的索引方式" class="headerlink" title="一、 Python可切片对象的索引方式"></a>一、 Python可切片对象的索引方式</h4><p>包括：正索引和负索引两部分，如下图所示，以list对象a = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]为例：</p><p><img src="https:////upload-images.jianshu.io/upload_images/14029140-3da45bbfe1029df4.jpg?imageMogr2/auto-orient/strip%7CimageView2/2/w/464/format/webp" alt="img"></p><p>python索引方式.jpg</p><h4 id="二、-Python切片操作的一般方式"><a href="#二、-Python切片操作的一般方式" class="headerlink" title="二、 Python切片操作的一般方式"></a>二、 Python切片操作的一般方式</h4><p>一个完整的切片表达式包含两个“:”，用于分隔三个参数(start_index、end_index、step)。当只有一个“:”时，默认第三个参数step=1；当一个“:”也没有时，start_index=end_index，表示切取start_index指定的那个元素。</p><figure class="highlight csharp"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">切片操作基本表达式：<span class="keyword">object</span>[start_index:end_index:step]</span><br></pre></td></tr></table></figure><p>step：正负数均可，其绝对值大小决定了切取数据时的‘‘步长”，而正负号决定了“切取方向”，正表示“从左往右”取值，负表示“从右往左”取值。当step省略时，默认为1，即从左往右以步长1取值。“切取方向非常重要！”“切取方向非常重要！”“切取方向非常重要！”，重要的事情说三遍！</p><p>start_index：表示起始索引（包含该索引对应值）；该参数省略时，表示从对象“端点”开始取值，至于是从“起点”还是从“终点”开始，则由step参数的正负决定，step为正从“起点”开始，为负从“终点”开始。</p><p>end_index：表示终止索引（不包含该索引对应值）；该参数省略时，表示一直取到数据“端点”，至于是到“起点”还是到“终点”，同样由step参数的正负决定，step为正时直到“终点”，为负时直到“起点”。</p><h4 id="三、-Python切片操作详细例子"><a href="#三、-Python切片操作详细例子" class="headerlink" title="三、 Python切片操作详细例子"></a>三、 Python切片操作详细例子</h4><p>以下示例均以list对象a = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]为例：</p><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a = [<span class="number">0</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>, <span class="number">8</span>, <span class="number">9</span>]</span><br></pre></td></tr></table></figure><h5 id="1-切取单个元素"><a href="#1-切取单个元素" class="headerlink" title="1. 切取单个元素"></a>1. 切取单个元素</h5><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="number">0</span>]</span><br><span class="line"><span class="meta">>></span>><span class="number">0</span></span><br><span class="line"><span class="meta">>></span>>a[-<span class="number">4</span>]</span><br><span class="line"><span class="meta">>></span>><span class="number">6</span></span><br><span class="line">当索引只有一个数时，表示切取某一个元素。</span><br></pre></td></tr></table></figure><h5 id="2-切取完整对象"><a href="#2-切取完整对象" class="headerlink" title="2. 切取完整对象"></a>2. 切取完整对象</h5><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="symbol">:</span>] <span class="comment">#从左往右</span></span><br><span class="line"><span class="meta">>></span>> [<span class="number">0</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>, <span class="number">8</span>, <span class="number">9</span>]</span><br><span class="line"><span class="meta">>></span>>a[<span class="symbol">:</span><span class="symbol">:</span>]<span class="comment">#从左往右</span></span><br><span class="line"><span class="meta">>></span>> [<span class="number">0</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>, <span class="number">8</span>, <span class="number">9</span>]</span><br><span class="line"><span class="meta">>></span>>a[<span class="symbol">:</span><span class="symbol">:-</span><span class="number">1</span>]<span class="comment">#从右往左</span></span><br><span class="line"><span class="meta">>></span>> [<span class="number">9</span>, <span class="number">8</span>, <span class="number">7</span>, <span class="number">6</span>, <span class="number">5</span>, <span class="number">4</span>, <span class="number">3</span>, <span class="number">2</span>, <span class="number">1</span>, <span class="number">0</span>]</span><br></pre></td></tr></table></figure><h5 id="3-start-index和end-index全为正（-）索引的情况"><a href="#3-start-index和end-index全为正（-）索引的情况" class="headerlink" title="3. start_index和end_index全为正（+）索引的情况"></a>3. start_index和end_index全为正（+）索引的情况</h5><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="number">1</span><span class="symbol">:</span><span class="number">6</span>]</span><br><span class="line"><span class="meta">>></span>> [<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>]</span><br><span class="line">step=<span class="number">1</span>，从左往右取值，start_index=<span class="number">1</span>到end_index=<span class="number">6</span>同样表示从左往右取值。</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="number">1</span><span class="symbol">:</span><span class="number">6</span><span class="symbol">:-</span><span class="number">1</span>]</span><br><span class="line"><span class="meta">>></span>> []</span><br><span class="line">输出为空列表，说明没取到数据。</span><br><span class="line">step=-<span class="number">1</span>，决定了从右往左取值，而start_index=<span class="number">1</span>到end_index=<span class="number">6</span>决定了从左往右取值，两者矛盾，所以为空。</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="number">6</span><span class="symbol">:</span><span class="number">2</span>]</span><br><span class="line"><span class="meta">>></span>> []</span><br><span class="line">同样输出为空列表。</span><br><span class="line">step=<span class="number">1</span>，决定了从左往右取值，而start_index=<span class="number">6</span>到end_index=<span class="number">2</span>决定了从右往左取值，两者矛盾，所以为空。</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="symbol">:</span><span class="number">6</span>]</span><br><span class="line"><span class="meta">>></span>> [<span class="number">0</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>]</span><br><span class="line">step=<span class="number">1</span>，表示从左往右取值，而start_index省略时，表示从端点开始，因此这里的端点是“起点”，即从“起点”值<span class="number">0</span>开始一直取到end_index=<span class="number">6</span>（该点不包括）。</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="symbol">:</span><span class="number">6</span><span class="symbol">:-</span><span class="number">1</span>]</span><br><span class="line"><span class="meta">>></span>> [<span class="number">9</span>, <span class="number">8</span>, <span class="number">7</span>]</span><br><span class="line">step=-<span class="number">1</span>，从右往左取值，而start_index省略时，表示从端点开始，因此这里的端点是“终点”，即从“终点”值<span class="number">9</span>开始一直取到end_index=<span class="number">6</span>（该点不包括）。</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="number">6</span><span class="symbol">:</span>]</span><br><span class="line"><span class="meta">>></span>> [<span class="number">6</span>, <span class="number">7</span>, <span class="number">8</span>, <span class="number">9</span>]</span><br><span class="line">step=<span class="number">1</span>，从左往右取值，从start_index=<span class="number">6</span>开始，一直取到“终点”值<span class="number">9</span>。</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="number">6</span><span class="symbol">:</span><span class="symbol">:-</span><span class="number">1</span>]</span><br><span class="line"><span class="meta">>></span>> [<span class="number">6</span>, <span class="number">5</span>, <span class="number">4</span>, <span class="number">3</span>, <span class="number">2</span>, <span class="number">1</span>, <span class="number">0</span>]</span><br><span class="line">step=-<span class="number">1</span>，从右往左取值，从start_index=<span class="number">6</span>开始，一直取到“起点”<span class="number">0</span>。</span><br></pre></td></tr></table></figure><h5 id="4-start-index和end-index全为负（-）索引的情况"><a href="#4-start-index和end-index全为负（-）索引的情况" class="headerlink" title="4. start_index和end_index全为负（-）索引的情况"></a>4. start_index和end_index全为负（-）索引的情况</h5><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[-<span class="number">1</span><span class="symbol">:-</span><span class="number">6</span>]</span><br><span class="line"><span class="meta">>></span>> []</span><br><span class="line">step=<span class="number">1</span>，从左往右取值，而start_index=-<span class="number">1</span>到end_index=-<span class="number">6</span>决定了从右往左取值，两者矛盾，所以为空。</span><br><span class="line">索引-<span class="number">1</span>在-<span class="number">6</span>的右边（如上图）</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[-<span class="number">1</span><span class="symbol">:-</span><span class="number">6</span><span class="symbol">:-</span><span class="number">1</span>]</span><br><span class="line"><span class="meta">>></span>> [<span class="number">9</span>, <span class="number">8</span>, <span class="number">7</span>, <span class="number">6</span>, <span class="number">5</span>]</span><br><span class="line">step=-<span class="number">1</span>，从右往左取值，start_index=-<span class="number">1</span>到end_index=-<span class="number">6</span>同样是从右往左取值。</span><br><span class="line">索引-<span class="number">1</span>在<span class="number">6</span>的右边（如上图）</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[-<span class="number">6</span><span class="symbol">:-</span><span class="number">1</span>]</span><br><span class="line"><span class="meta">>></span>> [<span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>, <span class="number">8</span>]</span><br><span class="line">step=<span class="number">1</span>，从左往右取值，而start_index=-<span class="number">6</span>到end_index=-<span class="number">1</span>同样是从左往右取值。</span><br><span class="line">索引-<span class="number">6</span>在-<span class="number">1</span>的左边（如上图）</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="symbol">:-</span><span class="number">6</span>]</span><br><span class="line"><span class="meta">>></span>> [<span class="number">0</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>]</span><br><span class="line">step=<span class="number">1</span>，从左往右取值，从“起点”开始一直取到end_index=-<span class="number">6</span>（该点不包括）。</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="symbol">:-</span><span class="number">6</span><span class="symbol">:-</span><span class="number">1</span>]</span><br><span class="line"><span class="meta">>></span>> [<span class="number">9</span>, <span class="number">8</span>, <span class="number">7</span>, <span class="number">6</span>, <span class="number">5</span>]</span><br><span class="line">step=-<span class="number">1</span>，从右往左取值，从“终点”开始一直取到end_index=-<span class="number">6</span>（该点不包括）。</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[-<span class="number">6</span><span class="symbol">:</span>]</span><br><span class="line"><span class="meta">>></span>> [<span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>, <span class="number">8</span>, <span class="number">9</span>]</span><br><span class="line">step=<span class="number">1</span>，从左往右取值，从start_index=-<span class="number">6</span>开始，一直取到“终点”。</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[-<span class="number">6</span><span class="symbol">:</span><span class="symbol">:-</span><span class="number">1</span>]</span><br><span class="line"><span class="meta">>></span>> [<span class="number">4</span>, <span class="number">3</span>, <span class="number">2</span>, <span class="number">1</span>, <span class="number">0</span>]</span><br><span class="line">step=-<span class="number">1</span>，从右往左取值，从start_index=-<span class="number">6</span>开始，一直取到“起点”。</span><br></pre></td></tr></table></figure><h5 id="5-start-index和end-index正（-）负（-）混合索引的情况"><a href="#5-start-index和end-index正（-）负（-）混合索引的情况" class="headerlink" title="5. start_index和end_index正（+）负（-）混合索引的情况"></a>5. start_index和end_index正（+）负（-）混合索引的情况</h5><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="number">1</span><span class="symbol">:-</span><span class="number">6</span>]</span><br><span class="line"><span class="meta">>></span>> [<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>]</span><br><span class="line">start_index=<span class="number">1</span>在end_index=-<span class="number">6</span>的左边，因此从左往右取值，而step=<span class="number">1</span>同样决定了从左往右取值，因此结果正确</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="number">1</span><span class="symbol">:-</span><span class="number">6</span><span class="symbol">:-</span><span class="number">1</span>]</span><br><span class="line"><span class="meta">>></span>> []</span><br><span class="line">start_index=<span class="number">1</span>在end_index=-<span class="number">6</span>的左边，因此从左往右取值，但step=-则决定了从右往左取值，两者矛盾，因此为空。</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[-<span class="number">1</span><span class="symbol">:</span><span class="number">6</span>]</span><br><span class="line"><span class="meta">>></span>> []</span><br><span class="line">start_index=-<span class="number">1</span>在end_index=<span class="number">6</span>的右边，因此从右往左取值，但step=<span class="number">1</span>则决定了从左往右取值，两者矛盾，因此为空。</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[-<span class="number">1</span><span class="symbol">:</span><span class="number">6</span><span class="symbol">:-</span><span class="number">1</span>]</span><br><span class="line"><span class="meta">>></span>> [<span class="number">9</span>, <span class="number">8</span>, <span class="number">7</span>]</span><br><span class="line">start_index=-<span class="number">1</span>在end_index=<span class="number">6</span>的右边，因此从右往左取值，而step=-<span class="number">1</span>同样决定了从右往左取值，因此结果正确。</span><br></pre></td></tr></table></figure><h5 id="6-多层切片操作"><a href="#6-多层切片操作" class="headerlink" title="6. 多层切片操作"></a>6. 多层切片操作</h5><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="symbol">:</span><span class="number">8</span>][<span class="number">2</span><span class="symbol">:</span><span class="number">5</span>][-<span class="number">1</span><span class="symbol">:</span>]</span><br><span class="line"><span class="meta">>></span>> [<span class="number">4</span>]</span><br><span class="line">相当于：</span><br><span class="line">a[<span class="symbol">:</span><span class="number">8</span>]=[<span class="number">0</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>]</span><br><span class="line">a[<span class="symbol">:</span><span class="number">8</span>][<span class="number">2</span><span class="symbol">:</span><span class="number">5</span>]= [<span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>]</span><br><span class="line">a[<span class="symbol">:</span><span class="number">8</span>][<span class="number">2</span><span class="symbol">:</span><span class="number">5</span>][-<span class="number">1</span><span class="symbol">:</span>] = [<span class="number">4</span>]</span><br><span class="line">理论上可无限次多层切片操作，只要上一次返回的是非空可切片对象即可。</span><br></pre></td></tr></table></figure><h5 id="7-切片操作的三个参数可以用表达式"><a href="#7-切片操作的三个参数可以用表达式" class="headerlink" title="7. 切片操作的三个参数可以用表达式"></a>7. 切片操作的三个参数可以用表达式</h5><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="number">2</span>+<span class="number">1</span><span class="symbol">:</span><span class="number">3</span>*<span class="number">2</span><span class="symbol">:</span><span class="number">7</span>%<span class="number">3</span>]</span><br><span class="line"><span class="meta">>></span>> [<span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>]</span><br><span class="line">即：a[<span class="number">2</span>+<span class="number">1</span><span class="symbol">:</span><span class="number">3</span>*<span class="number">2</span><span class="symbol">:</span><span class="number">7</span>%<span class="number">3</span>] = a[<span class="number">3</span><span class="symbol">:</span><span class="number">6</span><span class="symbol">:</span><span class="number">1</span>]</span><br></pre></td></tr></table></figure><h5 id="8-其他对象的切片操作"><a href="#8-其他对象的切片操作" class="headerlink" title="8. 其他对象的切片操作"></a>8. 其他对象的切片操作</h5><p>前面的切片操作以list对象为例进行说明，但实际上可进行切片操作的数据类型还有很多，包括元组、字符串等等。</p><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>> (<span class="number">0</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>)[<span class="symbol">:</span><span class="number">3</span>]</span><br><span class="line"><span class="meta">>></span>> (<span class="number">0</span>, <span class="number">1</span>, <span class="number">2</span>)</span><br><span class="line">元组的切片操作</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>><span class="string">'ABCDEFG'</span>[<span class="symbol">:</span><span class="symbol">:</span><span class="number">2</span>]</span><br><span class="line"><span class="meta">>></span>><span class="string">'ACEG'</span></span><br><span class="line">字符串的切片操作</span><br></pre></td></tr></table></figure><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>for i in range(<span class="number">1</span>,<span class="number">100</span>)[<span class="number">2</span><span class="symbol">:</span><span class="symbol">:</span><span class="number">3</span>][-<span class="number">5</span><span class="symbol">:</span>]: </span><br><span class="line"> print(i)</span><br><span class="line"><span class="meta">>></span>><span class="number">87</span></span><br><span class="line"><span class="number">90</span></span><br><span class="line"><span class="number">93</span></span><br><span class="line"><span class="number">96</span></span><br><span class="line"><span class="number">99</span></span><br><span class="line">就是利用range()函数生成<span class="number">1</span>-<span class="number">99</span>的整数，然后从start_index=<span class="number">2</span>（即<span class="number">3</span>）开始以step=<span class="number">3</span>取值，直到终点，再在新序列中取最后五个数。</span><br></pre></td></tr></table></figure><h4 id="四、-常用切片操作"><a href="#四、-常用切片操作" class="headerlink" title="四、 常用切片操作"></a>四、 常用切片操作</h4><h5 id="1-取偶数位置"><a href="#1-取偶数位置" class="headerlink" title="1.取偶数位置"></a>1.取偶数位置</h5><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>b = a[<span class="symbol">:</span><span class="symbol">:</span><span class="number">2</span>]</span><br><span class="line">[<span class="number">0</span>, <span class="number">2</span>, <span class="number">4</span>, <span class="number">6</span>, <span class="number">8</span>]</span><br></pre></td></tr></table></figure><h5 id="2-取奇数位置"><a href="#2-取奇数位置" class="headerlink" title="2.取奇数位置"></a>2.取奇数位置</h5><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>b = a[<span class="number">1</span><span class="symbol">:</span><span class="symbol">:</span><span class="number">2</span>]</span><br><span class="line">[<span class="number">1</span>, <span class="number">3</span>, <span class="number">5</span>, <span class="number">7</span>, <span class="number">9</span>]</span><br></pre></td></tr></table></figure><h5 id="3-拷贝整个对象"><a href="#3-拷贝整个对象" class="headerlink" title="3.拷贝整个对象"></a>3.拷贝整个对象</h5><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>b = a[<span class="symbol">:</span>] <span class="comment">#</span></span><br><span class="line"><span class="meta">>></span>>print(b) <span class="comment">#[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]</span></span><br><span class="line"><span class="meta">>></span>>print(id(a)) <span class="comment">#41946376</span></span><br><span class="line"><span class="meta">>></span>>print(id(b)) <span class="comment">#41921864</span></span><br><span class="line">或</span><br><span class="line"><span class="meta">>></span>>b = a.copy()</span><br><span class="line"><span class="meta">>></span>>print(b) <span class="comment">#[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]</span></span><br><span class="line"><span class="meta">>></span>>print(id(a)) <span class="comment">#39783752</span></span><br><span class="line"><span class="meta">>></span>>print(id(b)) <span class="comment">#39759176</span></span><br></pre></td></tr></table></figure><p>需要注意的是：<strong>[:]和.copy()都属于“浅拷贝”，只拷贝最外层元素，内层嵌套元素则通过引用方式共享，而非独立分配内存</strong>，如果需要彻底拷贝则需采用“深拷贝”方式，如下例所示：</p><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a = [<span class="number">1</span>,<span class="number">2</span>,[<span class="string">'A'</span>,<span class="string">'B'</span>]]</span><br><span class="line"><span class="meta">>></span>>print(<span class="string">'a={}'</span>.format(a))</span><br><span class="line"><span class="meta">>></span>>b = a[<span class="symbol">:</span>]</span><br><span class="line"><span class="meta">>></span>>b[<span class="number">0</span>] = <span class="number">9</span> <span class="comment">#修改b的最外层元素，将1变成9</span></span><br><span class="line"><span class="meta">>></span>>b[<span class="number">2</span>][<span class="number">0</span>] = <span class="string">'D'</span> <span class="comment">#修改b的内嵌层元素</span></span><br><span class="line"><span class="meta">>></span>>print(<span class="string">'a={}'</span>.format(a))</span><br><span class="line"><span class="meta">>></span>>print(<span class="string">'b={}'</span>.format(b))</span><br><span class="line"><span class="meta">>></span>>print(<span class="string">'id(a)={}'</span>.format(id(a)))</span><br><span class="line"><span class="meta">>></span>>print(<span class="string">'id(b)={}'</span>.format(id(b)))</span><br><span class="line">a=[<span class="number">1</span>, <span class="number">2</span>, [<span class="string">'A'</span>, <span class="string">'B'</span>]] <span class="comment">#原始a</span></span><br><span class="line">a=[<span class="number">1</span>, <span class="number">2</span>, [<span class="string">'D'</span>, <span class="string">'B'</span>]] <span class="comment">#b修改内部元素A为D后，a中的A也变成了D，说明共享内部嵌套元素，但外部元素1没变。</span></span><br><span class="line">b=[<span class="number">9</span>, <span class="number">2</span>, [<span class="string">'D'</span>, <span class="string">'B'</span>]] <span class="comment">#修改后的b</span></span><br><span class="line">id(a)=<span class="number">38669128</span></span><br><span class="line">id(b)=<span class="number">38669192</span></span><br></pre></td></tr></table></figure><h5 id="4-修改单个元素"><a href="#4-修改单个元素" class="headerlink" title="4.修改单个元素"></a>4.修改单个元素</h5><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="number">3</span>] = [<span class="string">'A'</span>,<span class="string">'B'</span>]</span><br><span class="line">[<span class="number">0</span>, <span class="number">1</span>, <span class="number">2</span>, [<span class="string">'A'</span>, <span class="string">'B'</span>], <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>, <span class="number">8</span>, <span class="number">9</span>]</span><br></pre></td></tr></table></figure><h5 id="5-在某个位置插入元素"><a href="#5-在某个位置插入元素" class="headerlink" title="5.在某个位置插入元素"></a>5.在某个位置插入元素</h5><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="number">3</span><span class="symbol">:</span><span class="number">3</span>] = [<span class="string">'A'</span>,<span class="string">'B'</span>,<span class="string">'C'</span>]</span><br><span class="line">[<span class="number">0</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="string">'A'</span>, <span class="string">'B'</span>, <span class="string">'C'</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>, <span class="number">8</span>, <span class="number">9</span>]</span><br><span class="line"><span class="meta">>></span>>a[<span class="number">0</span><span class="symbol">:</span><span class="number">0</span>] = [<span class="string">'A'</span>,<span class="string">'B'</span>]</span><br><span class="line">[<span class="string">'A'</span>, <span class="string">'B'</span>, <span class="number">0</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>, <span class="number">6</span>, <span class="number">7</span>, <span class="number">8</span>, <span class="number">9</span>]</span><br></pre></td></tr></table></figure><h5 id="6-替换一部分元素"><a href="#6-替换一部分元素" class="headerlink" title="6.替换一部分元素"></a>6.替换一部分元素</h5><figure class="highlight ruby"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">>></span>>a[<span class="number">3</span><span class="symbol">:</span><span class="number">6</span>] = [<span class="string">'A'</span>,<span class="string">'B'</span>]</span><br><span class="line">[<span class="number">0</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="string">'A'</span>, <span class="string">'B'</span>, <span class="number">6</span>, <span class="number">7</span>, <span class="number">8</span>, <span class="number">9</span>]</span><br></pre></td></tr></table></figure><h4 id="五、-总结"><a href="#五、-总结" class="headerlink" title="五、 总结"></a>五、 总结</h4><p>（一）start_index、end_index、step三者可同为正、同为负，或正负混合。但必须遵循一个原则，即：当start_index表示的实际位置在end_index的左边时，从左往右取值，此时step必须是正数（同样表示从左往右）；当start_index表示的实际位置在end_index的右边时，表示从右往左取值，此时step必须是负数（同样表示从右往左），即两者的取值顺序必须相同。</p><p>（二）当start_index或end_index省略时，取值的起始索引和终止索引由step的正负来决定，这种情况不会有取值方向矛盾（即不会返回空列表[]），但正和负取到的结果顺序是相反的，因为一个向左一个向右。</p><p>（三）step的正负是必须要考虑的，尤其是当step省略时。比如a[-1:]，很容易就误认为是从“终点”开始一直取到“起点”，即a[-1:]= [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]，但实际上a[-1:]=[9]（注意不是9），原因在于step省略时step=1表示从左往右取值，而起始索引start_index=-1本身就是对象的最右边元素了，再往右已经没数据了，因此结果只含有9一个元素。</p><p>（四）需要注意：“取单个元素（不带“:”）”时，返回的是对象的某个元素，其类型由元素本身的类型决定，而与母对象无关，如上面的a[0]=0、a[-4]=6，元素0和6都是“数值型”，而母对象a却是“list”型；“取连续切片（带“:”）”时，返回结果的类型与母对象相同，哪怕切取的连续切片只包含一个元素，如上面的a[-1:]=[9]，返回的是一个只包含元素“9”的list，而非数值型“9”。</p><p><a href="https://www.jianshu.com/p/15715d6f4dad" target="_blank" rel="noopener">原文链接</a></p>]]></content>
<summary type="html"><h4 id="写在前面："><a href="#写在前面：" class="headerlink" title="写在前面："></a>写在前面：</h4><p>利用python解决问题的过程中，经常会遇到从某个对象中抽取部分值的情况。“切片”操作正是专门用于实现这一目标的有力</summary>
<category term="python基础" scheme="https://wicherqaq.github.io/categories/python%E5%9F%BA%E7%A1%80/"/>
</entry>
<entry>
<title>清华开源镜像站的使用</title>
<link href="https://wicherqaq.github.io/2020/09/16/%E6%B8%85%E5%8D%8E%E5%BC%80%E6%BA%90%E9%95%9C%E5%83%8F%E7%AB%99%E7%9A%84%E4%BD%BF%E7%94%A8/"/>
<id>https://wicherqaq.github.io/2020/09/16/%E6%B8%85%E5%8D%8E%E5%BC%80%E6%BA%90%E9%95%9C%E5%83%8F%E7%AB%99%E7%9A%84%E4%BD%BF%E7%94%A8/</id>
<published>2020-09-16T07:17:43.000Z</published>
<updated>2020-09-16T07:19:43.477Z</updated>
<content type="html"><![CDATA[<p><a href="https://mirror.tuna.tsinghua.edu.cn/help/anaconda/" target="_blank" rel="noopener">源链接https://mirror.tuna.tsinghua.edu.cn/help/anaconda/</a></p><h2 id="Anaconda-镜像使用帮助"><a href="#Anaconda-镜像使用帮助" class="headerlink" title="Anaconda 镜像使用帮助"></a>Anaconda 镜像使用帮助</h2><p>Anaconda 是一个用于科学计算的 Python 发行版，支持 Linux, Mac, Windows, 包含了众多流行的科学计算、数据分析的 Python 包。</p><p>Anaconda 安装包可以到 <a href="https://mirrors.tuna.tsinghua.edu.cn/anaconda/archive/" target="_blank" rel="noopener">https://mirrors.tuna.tsinghua.edu.cn/anaconda/archive/</a> 下载。</p><p>TUNA 还提供了 Anaconda 仓库与第三方源（conda-forge、msys2、pytorch等，<a href="https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/" target="_blank" rel="noopener">查看完整列表</a>）的镜像，各系统都可以通过修改用户目录下的 <code>.condarc</code> 文件。Windows 用户无法直接创建名为 <code>.condarc</code> 的文件，可先执行 <code>conda config --set show_channel_urls yes</code> 生成该文件之后再修改。</p><p>注：由于更新过快难以同步，我们不同步<code>pytorch-nightly</code>, <code>pytorch-nightly-cpu</code>, <code>ignite-nightly</code>这三个包。</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">channels:</span><br><span class="line"> - defaults</span><br><span class="line">show_channel_urls: true</span><br><span class="line">channel_alias: https://mirrors.tuna.tsinghua.edu.cn/anaconda</span><br><span class="line">default_channels:</span><br><span class="line"> - https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/main</span><br><span class="line"> - https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/free</span><br><span class="line"> - https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/r</span><br><span class="line"> - https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/pro</span><br><span class="line"> - https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/msys2</span><br><span class="line">custom_channels:</span><br><span class="line"> conda-forge: https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud</span><br><span class="line"> msys2: https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud</span><br><span class="line"> bioconda: https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud</span><br><span class="line"> menpo: https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud</span><br><span class="line"> pytorch: https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud</span><br><span class="line"> simpleitk: https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud</span><br></pre></td></tr></table></figure><p>即可添加 Anaconda Python 免费仓库。</p><p>运行 <code>conda clean -i</code> 清除索引缓存，保证用的是镜像站提供的索引。</p><p>运行 <code>conda create -n myenv numpy</code> 测试一下吧。</p><h2 id="Miniconda-镜像使用帮助"><a href="#Miniconda-镜像使用帮助" class="headerlink" title="Miniconda 镜像使用帮助"></a>Miniconda 镜像使用帮助</h2><p>Miniconda 是一个 Anaconda 的轻量级替代，默认只包含了 python 和 conda，但是可以通过 pip 和 conda 来安装所需要的包。</p><p>Miniconda 安装包可以到 <a href="https://mirrors.tuna.tsinghua.edu.cn/anaconda/miniconda/" target="_blank" rel="noopener">https://mirrors.tuna.tsinghua.edu.cn/anaconda/miniconda/</a> 下载。</p><h3 id="其他三方源"><a href="#其他三方源" class="headerlink" title="其他三方源"></a>其他三方源</h3><p>对于conda的其他三方源，如有需要请修改<a href="https://github.com/tuna/tunasync-scripts/blob/master/anaconda.py" target="_blank" rel="noopener">anaconda.py</a>文件，并提交pull request，我们会综合考虑多方因素来酌情增减。</p>]]></content>
<summary type="html"><p><a href="https://mirror.tuna.tsinghua.edu.cn/help/anaconda/" target="_blank" rel="noopener">源链接https://mirror.tuna.tsinghua.edu.cn/help/a</summary>
<category term="机器学习" scheme="https://wicherqaq.github.io/categories/%E6%9C%BA%E5%99%A8%E5%AD%A6%E4%B9%A0/"/>
<category term="环境搭建" scheme="https://wicherqaq.github.io/tags/%E7%8E%AF%E5%A2%83%E6%90%AD%E5%BB%BA/"/>
</entry>
<entry>
<title>python入门（下）</title>
<link href="https://wicherqaq.github.io/2020/09/15/python%E5%85%A5%E9%97%A8%EF%BC%88%E4%B8%8B%EF%BC%89/"/>
<id>https://wicherqaq.github.io/2020/09/15/python%E5%85%A5%E9%97%A8%EF%BC%88%E4%B8%8B%EF%BC%89/</id>
<published>2020-09-15T01:12:47.000Z</published>
<updated>2020-09-15T01:13:22.273Z</updated>
<content type="html"><![CDATA[<h1 id="Python入门-下"><a href="#Python入门-下" class="headerlink" title="Python入门(下)"></a>Python入门(下)</h1><ol><li><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#简介" target="_blank" rel="noopener">简介</a></li><li><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#函数" target="_blank" rel="noopener">函数</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#函数的定义" target="_blank" rel="noopener">1. 函数的定义</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#函数的调用" target="_blank" rel="noopener">2. 函数的调用</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#函数文档" target="_blank" rel="noopener">3. 函数文档</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#函数参数" target="_blank" rel="noopener">4. 函数参数</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#函数的返回值" target="_blank" rel="noopener">5. 函数的返回值</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#变量作用域" target="_blank" rel="noopener">6. 变量作用域</a></li><li><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#Lambda-表达式" target="_blank" rel="noopener">Lambda-表达式</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#匿名函数的定义" target="_blank" rel="noopener">1. 匿名函数的定义</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#匿名函数的应用" target="_blank" rel="noopener">2. 匿名函数的应用</a></li><li><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#类与对象" target="_blank" rel="noopener">类与对象</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#属性和方法组成对象" target="_blank" rel="noopener">1. 属性和方法组成对象</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#self-是什么？" target="_blank" rel="noopener">2. self是什么？</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#Python-的魔法方法" target="_blank" rel="noopener">3. Python的魔法方法</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#公有和私有" target="_blank" rel="noopener">4. 公有和私有</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#继承" target="_blank" rel="noopener">5. 继承</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#组合" target="_blank" rel="noopener">6. 组合</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#类、类对象和实例对象" target="_blank" rel="noopener">7. 类、类对象和实例对象</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#什么是绑定？" target="_blank" rel="noopener">8. 什么是绑定？</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#一些相关的内置函数（BIF）" target="_blank" rel="noopener">9. 一些相关的内置函数（BIF）</a></li><li><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#魔法方法" target="_blank" rel="noopener">魔法方法</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#基本的魔法方法" target="_blank" rel="noopener">1. 基本的魔法方法</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#算术运算符" target="_blank" rel="noopener">2. 算术运算符</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#反算术运算符" target="_blank" rel="noopener">3. 反算术运算符</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#增量赋值运算符" target="_blank" rel="noopener">4. 增量赋值运算</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#一元运算符" target="_blank" rel="noopener">5. 一元运算符</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#属性访问" target="_blank" rel="noopener">6. 属性访问</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#描述符" target="_blank" rel="noopener">7. 描述符</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#定制序列" target="_blank" rel="noopener">8. 定制序列</a><br><a href="https://dsw2-dsw-d20200915091044ef48ed9fd208000141783-8888.pcs-gw-cn-shanghai.aliyun.com/lab#迭代器" target="_blank" rel="noopener">9. 迭代器</a></li></ol><h1 id="简介"><a href="#简介" class="headerlink" title="简介"></a>简介</h1><p>Python 是一种通用编程语言，其在科学计算和机器学习领域具有广泛的应用。如果我们打算利用 Python 来执行机器学习，那么对 Python 有一些基本的了解就是至关重要的。本 Python 入门系列体验就是为这样的初学者精心准备的。</p><p>本实验包括以下内容：</p><ul><li>函数<ul><li>函数的定义</li><li>函数的调用</li><li>函数文档</li><li>函数参数</li><li>函数的返回值</li><li>变量作用域</li></ul></li><li>Lambda 表达式<ul><li>匿名函数的定义</li><li>匿名函数的应用</li></ul></li><li>类与对象<ul><li>对象 = 属性 + 方法</li><li>self 是什么？</li><li>Python 的魔法方法</li><li>公有和私有</li><li>继承</li><li>组合</li><li>类、类对象和实例对象</li><li>什么是绑定？</li><li>一些相关的内置函数（BIF）</li></ul></li><li>魔法方法<ul><li>基本的魔法方法</li><li>算术运算符</li><li>反算术运算符</li><li>增量赋值运算符</li><li>一元运算符</li><li>属性访问</li><li>描述符</li><li>定制序列</li><li>迭代器</li></ul></li></ul><h1 id="函数"><a href="#函数" class="headerlink" title="函数"></a>函数</h1><h2 id="函数的定义"><a href="#函数的定义" class="headerlink" title="函数的定义"></a>函数的定义</h2><p>还记得 Python 里面“万物皆对象”么？Python 把函数也当成对象，可以从另一个函数中返回出来而去构建高阶函数，比如： 参数是函数、返回值是函数。</p><p>我们首先来介绍函数的定义。</p><ul><li>函数以<code>def</code>关键词开头，后接函数名和圆括号()。</li><li>函数执行的代码以冒号起始，并且缩进。</li><li>return [表达式] 结束函数，选择性地返回一个值给调用方。不带表达式的return相当于返回<code>None</code>。</li></ul><blockquote><p>def functionname (parameters):<br> “函数_文档字符串”<br> function_suite<br> return [expression]</p></blockquote><h2 id="函数的调用"><a href="#函数的调用" class="headerlink" title="函数的调用"></a>函数的调用</h2><p>【例子】</p><p>[1]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">def printme(str):</span><br><span class="line"> print(str)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">printme("我要调用用户自定义函数!") # 我要调用用户自定义函数!</span><br><span class="line">printme("再次调用同一函数") # 再次调用同一函数</span><br><span class="line">temp = printme('hello') # hello</span><br><span class="line">print(temp) # None</span><br><span class="line">我要调用用户自定义函数!</span><br><span class="line">再次调用同一函数</span><br><span class="line">hello</span><br><span class="line">None</span><br></pre></td></tr></table></figure><h2 id="函数文档"><a href="#函数文档" class="headerlink" title="函数文档"></a>函数文档</h2><p>[2]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line">def MyFirstFunction(name):</span><br><span class="line"> "函数定义过程中name是形参"</span><br><span class="line"> # 因为Ta只是一个形式，表示占据一个参数位置</span><br><span class="line"> print('传递进来的{0}叫做实参，因为Ta是具体的参数值！'.format(name))</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">MyFirstFunction('老马的程序人生') </span><br><span class="line"># 传递进来的老马的程序人生叫做实参，因为Ta是具体的参数值！</span><br><span class="line"></span><br><span class="line">print(MyFirstFunction.__doc__) </span><br><span class="line"># 函数定义过程中name是形参</span><br><span class="line"></span><br><span class="line">help(MyFirstFunction)</span><br><span class="line"># Help on function MyFirstFunction in module __main__:</span><br><span class="line"># MyFirstFunction(name)</span><br><span class="line"># 函数定义过程中name是形参</span><br><span class="line">传递进来的老马的程序人生叫做实参，因为Ta是具体的参数值！</span><br><span class="line">函数定义过程中name是形参</span><br><span class="line">Help on function MyFirstFunction in module __main__:</span><br><span class="line"></span><br><span class="line">MyFirstFunction(name)</span><br><span class="line"> 函数定义过程中name是形参</span><br></pre></td></tr></table></figure><h2 id="函数参数"><a href="#函数参数" class="headerlink" title="函数参数"></a>函数参数</h2><p>Python 的函数具有非常灵活多样的参数形态，既可以实现简单的调用，又可以传入非常复杂的参数。从简到繁的参数形态如下：</p><ul><li>位置参数 (positional argument)</li><li>默认参数 (default argument)</li><li>可变参数 (variable argument)</li><li>关键字参数 (keyword argument)</li><li>命名关键字参数 (name keyword argument)</li><li>参数组合</li></ul><p><strong>1. 位置参数</strong></p><blockquote><p>def functionname(arg1):<br> “函数_文档字符串”<br> function_suite<br> return [expression]</p></blockquote><ul><li><code>arg1</code> - 位置参数 ，这些参数在调用函数 (call function) 时位置要固定。</li></ul><p><strong>2. 默认参数</strong></p><blockquote><p>def functionname(arg1, arg2=v):<br> “函数_文档字符串”<br> function_suite<br> return [expression]</p></blockquote><ul><li><code>arg2 = v</code> - 默认参数 = 默认值，调用函数时，默认参数的值如果没有传入，则被认为是默认值。</li><li>默认参数一定要放在位置参数 <strong>后面</strong>，不然程序会报错。</li></ul><p>【例子】</p><p>[3]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">def printinfo(name, age=8):</span><br><span class="line"> print('Name:{0},Age:{1}'.format(name, age))</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">printinfo('小马') # Name:小马,Age:8</span><br><span class="line">printinfo('小马', 10) # Name:小马,Age:10</span><br><span class="line">Name:小马,Age:8</span><br><span class="line">Name:小马,Age:10</span><br></pre></td></tr></table></figure><ul><li>Python 允许函数调用时参数的顺序与声明时不一致，因为 Python 解释器能够用参数名匹配参数值。</li></ul><p>【例子】</p><p>[4]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">def printinfo(name, age):</span><br><span class="line"> print('Name:{0},Age:{1}'.format(name, age))</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">printinfo(age=8, name='小马') # Name:小马,Age:8</span><br><span class="line">Name:小马,Age:8</span><br></pre></td></tr></table></figure><p><strong>3. 可变参数</strong></p><p>顾名思义，可变参数就是传入的参数个数是可变的，可以是 0, 1, 2 到任意个，是不定长的参数。</p><blockquote><p>def functionname(arg1, arg2=v, *args):<br> “函数_文档字符串”<br> function_suite<br> return [expression]</p></blockquote><ul><li><code>*args</code> - 可变参数，可以是从零个到任意个，自动组装成元组。</li><li>加了星号（*）的变量名会存放所有未命名的变量参数。</li></ul><p>【例子】</p><p>[5]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">def printinfo(arg1, *args):</span><br><span class="line"> print(arg1)</span><br><span class="line"> for var in args:</span><br><span class="line"> print(var)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">printinfo(10) # 10</span><br><span class="line">printinfo(70, 60, 50)</span><br><span class="line"># 70</span><br><span class="line"># 60</span><br><span class="line"># 50</span><br><span class="line">10</span><br><span class="line">70</span><br><span class="line">60</span><br><span class="line">50</span><br></pre></td></tr></table></figure><p><strong>4. 关键字参数</strong></p><blockquote><p>def functionname(arg1, arg2=v, <em>args, *</em>kw):<br> “函数_文档字符串”<br> function_suite<br> return [expression]</p></blockquote><ul><li><code>**kw</code> - 关键字参数，可以是从零个到任意个，自动组装成字典。</li></ul><p>【例子】</p><p>[6]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line">def printinfo(arg1, *args, **kwargs):</span><br><span class="line"> print(arg1)</span><br><span class="line"> print(args)</span><br><span class="line"> print(kwargs)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">printinfo(70, 60, 50)</span><br><span class="line"># 70</span><br><span class="line"># (60, 50)</span><br><span class="line"># {}</span><br><span class="line">printinfo(70, 60, 50, a=1, b=2)</span><br><span class="line"># 70</span><br><span class="line"># (60, 50)</span><br><span class="line"># {'a': 1, 'b': 2}</span><br><span class="line">70</span><br><span class="line">(60, 50)</span><br><span class="line">{}</span><br><span class="line">70</span><br><span class="line">(60, 50)</span><br><span class="line">{'a': 1, 'b': 2}</span><br></pre></td></tr></table></figure><p>「可变参数」和「关键字参数」的同异总结如下：</p><ul><li>可变参数允许传入零个到任意个参数，它们在函数调用时自动组装为一个元组 (tuple)。</li><li>关键字参数允许传入零个到任意个参数，它们在函数内部自动组装为一个字典 (dict)。</li></ul><p><strong>5. 命名关键字参数</strong></p><blockquote><p>def functionname(arg1, arg2=v, <em>args, \</em>, nkw, **kw):<br> “函数_文档字符串”<br> function_suite<br> return [expression]</p></blockquote><ul><li><code>*, nkw</code> - 命名关键字参数，用户想要输入的关键字参数，定义方式是在nkw 前面加个分隔符 <code>*</code>。</li><li>如果要限制关键字参数的名字，就可以用「命名关键字参数」</li><li>使用命名关键字参数时，要特别注意不能缺少参数名。</li></ul><p>【例子】</p><p>[8]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line">def printinfo(arg1, *, nkw, **kwargs):</span><br><span class="line"> print(arg1)</span><br><span class="line"> print(nkw)</span><br><span class="line"> print(kwargs)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">printinfo(70, nkw=10, a=1, b=2)</span><br><span class="line"># 70</span><br><span class="line"># 10</span><br><span class="line"># {'a': 1, 'b': 2}</span><br><span class="line"></span><br><span class="line">printinfo(70, 10, a=1, b=2)</span><br><span class="line"># TypeError: printinfo() takes 1 positional argument but 2 were given</span><br><span class="line">70</span><br><span class="line">10</span><br><span class="line">{'a': 1, 'b': 2}</span><br></pre></td></tr></table></figure><ul><li>没有写参数名<code>nwk</code>，因此 10 被当成「位置参数」，而原函数只有 1 个位置函数，现在调用了 2 个，因此程序会报错。</li></ul><p><strong>6. 参数组合</strong></p><p>在 Python 中定义函数，可以用位置参数、默认参数、可变参数、命名关键字参数和关键字参数，这 5 种参数中的 4 个都可以一起使用，但是注意，参数定义的顺序必须是：</p><ul><li>位置参数、默认参数、可变参数和关键字参数。</li><li>位置参数、默认参数、命名关键字参数和关键字参数。</li></ul><p>要注意定义可变参数和关键字参数的语法：</p><ul><li><code>*args</code> 是可变参数，<code>args</code> 接收的是一个 <code>tuple</code></li><li><code>**kw</code> 是关键字参数，<code>kw</code> 接收的是一个 <code>dict</code></li></ul><p>命名关键字参数是为了限制调用者可以传入的参数名，同时可以提供默认值。定义命名关键字参数不要忘了写分隔符 <code>*</code>，否则定义的是位置参数。</p><p>警告：虽然可以组合多达 5 种参数，但不要同时使用太多的组合，否则函数很难懂。</p><h2 id="函数的返回值"><a href="#函数的返回值" class="headerlink" title="函数的返回值"></a>函数的返回值</h2><p>【例子】</p><p>[9]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">def add(a, b):</span><br><span class="line"> return a + b</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">print(add(1, 2)) # 3</span><br><span class="line">print(add([1, 2, 3], [4, 5, 6])) # [1, 2, 3, 4, 5, 6]</span><br><span class="line">3</span><br><span class="line">[1, 2, 3, 4, 5, 6]</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[10]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">def back():</span><br><span class="line"> return [1, '小马的程序人生', 3.14]</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">print(back()) # [1, '小马的程序人生', 3.14]</span><br><span class="line">[1, '小马的程序人生', 3.14]</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[11]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">def back():</span><br><span class="line"> return 1, '小马的程序人生', 3.14</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">print(back()) # (1, '小马的程序人生', 3.14)</span><br><span class="line">(1, '小马的程序人生', 3.14)</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[12]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">def printme(str):</span><br><span class="line"> print(str)</span><br><span class="line"></span><br><span class="line">temp = printme('hello') # hello</span><br><span class="line">print(temp) # None</span><br><span class="line">print(type(temp)) # <class 'NoneType'></span><br><span class="line">hello</span><br><span class="line">None</span><br><span class="line"><class 'NoneType'></span><br></pre></td></tr></table></figure><h2 id="变量作用域"><a href="#变量作用域" class="headerlink" title="变量作用域"></a>变量作用域</h2><ul><li>Python 中，程序的变量并不是在哪个位置都可以访问的，访问权限决定于这个变量是在哪里赋值的。</li><li>定义在函数内部的变量拥有局部作用域，该变量称为局部变量。</li><li>定义在函数外部的变量拥有全局作用域，该变量称为全局变量。</li><li>局部变量只能在其被声明的函数内部访问，而全局变量可以在整个程序范围内访问。</li></ul><p>【例子】</p><p>[13]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">def discounts(price, rate):</span><br><span class="line"> final_price = price * rate</span><br><span class="line"> return final_price</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">old_price = float(input('请输入原价:')) # 98</span><br><span class="line">rate = float(input('请输入折扣率:')) # 0.9</span><br><span class="line">new_price = discounts(old_price, rate)</span><br><span class="line">print('打折后价格是:%.2f' % new_price) # 88.20</span><br><span class="line">请输入原价:98</span><br><span class="line">请输入折扣率:0.9</span><br><span class="line">打折后价格是:88.20</span><br></pre></td></tr></table></figure><ul><li>当内部作用域想修改外部作用域的变量时，就要用到<code>global</code>和<code>nonlocal</code>关键字了。</li></ul><p>【例子】</p><p>[14]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">num = 1</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">def fun1():</span><br><span class="line"> global num # 需要使用 global 关键字声明</span><br><span class="line"> print(num) # 1</span><br><span class="line"> num = 123</span><br><span class="line"> print(num) # 123</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">fun1()</span><br><span class="line">print(num) # 123</span><br><span class="line">1</span><br><span class="line">123</span><br><span class="line">123</span><br></pre></td></tr></table></figure><p><strong>内嵌函数</strong></p><p>【例子】</p><p>[15]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">def outer():</span><br><span class="line"> print('outer函数在这被调用')</span><br><span class="line"></span><br><span class="line"> def inner():</span><br><span class="line"> print('inner函数在这被调用')</span><br><span class="line"></span><br><span class="line"> inner() # 该函数只能在outer函数内部被调用</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">outer()</span><br><span class="line"># outer函数在这被调用</span><br><span class="line"># inner函数在这被调用</span><br><span class="line">outer函数在这被调用</span><br><span class="line">inner函数在这被调用</span><br></pre></td></tr></table></figure><p><strong>闭包</strong></p><ul><li>是函数式编程的一个重要的语法结构，是一种特殊的内嵌函数。</li><li>如果在一个内部函数里对外层非全局作用域的变量进行引用，那么内部函数就被认为是闭包。</li><li>通过闭包可以访问外层非全局作用域的变量，这个作用域称为 <strong>闭包作用域</strong>。</li></ul><p>【例子】</p><p>[16]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">def funX(x):</span><br><span class="line"> def funY(y):</span><br><span class="line"> return x * y</span><br><span class="line"></span><br><span class="line"> return funY</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">i = funX(8)</span><br><span class="line">print(type(i)) # <class 'function'></span><br><span class="line">print(i(5)) # 40</span><br><span class="line"><class 'function'></span><br><span class="line">40</span><br></pre></td></tr></table></figure><p>【例子】闭包的返回值通常是函数。</p><p>[17]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line">def make_counter(init):</span><br><span class="line"> counter = [init]</span><br><span class="line"></span><br><span class="line"> def inc(): counter[0] += 1</span><br><span class="line"></span><br><span class="line"> def dec(): counter[0] -= 1</span><br><span class="line"></span><br><span class="line"> def get(): return counter[0]</span><br><span class="line"></span><br><span class="line"> def reset(): counter[0] = init</span><br><span class="line"></span><br><span class="line"> return inc, dec, get, reset</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">inc, dec, get, reset = make_counter(0)</span><br><span class="line">inc()</span><br><span class="line">inc()</span><br><span class="line">inc()</span><br><span class="line">print(get()) # 3</span><br><span class="line">dec()</span><br><span class="line">print(get()) # 2</span><br><span class="line">reset()</span><br><span class="line">print(get()) # 0</span><br><span class="line">3</span><br><span class="line">2</span><br><span class="line">0</span><br></pre></td></tr></table></figure><p>【例子】 如果要修改闭包作用域中的变量则需要 <code>nonlocal</code> 关键字</p><p>[18]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">def outer():</span><br><span class="line"> num = 10</span><br><span class="line"></span><br><span class="line"> def inner():</span><br><span class="line"> nonlocal num # nonlocal关键字声明</span><br><span class="line"> num = 100</span><br><span class="line"> print(num)</span><br><span class="line"></span><br><span class="line"> inner()</span><br><span class="line"> print(num)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">outer()</span><br><span class="line"></span><br><span class="line"># 100</span><br><span class="line"># 100</span><br><span class="line">100</span><br><span class="line">100</span><br></pre></td></tr></table></figure><p><strong>递归</strong></p><ul><li>如果一个函数在内部调用自身本身，这个函数就是递归函数。</li></ul><p>【例子】<code>n! = 1 x 2 x 3 x ... x n</code></p><p>[20]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"># 利用循环</span><br><span class="line">n = 5</span><br><span class="line">for k in range(1, 5):</span><br><span class="line"> n = n * k</span><br><span class="line">print(n) # 120</span><br><span class="line"></span><br><span class="line"># 利用递归</span><br><span class="line">def factorial(n):</span><br><span class="line"> if n == 1:</span><br><span class="line"> return 1</span><br><span class="line"> return n * factorial(n - 1)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">print(factorial(5)) # 120</span><br><span class="line">120</span><br><span class="line">120</span><br></pre></td></tr></table></figure><p>【例子】斐波那契数列 <code>f(n)=f(n-1)+f(n-2), f(0)=0 f(1)=1</code></p><p>[21]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line"># 利用循环</span><br><span class="line">i = 0</span><br><span class="line">j = 1</span><br><span class="line">lst = list([i, j])</span><br><span class="line">for k in range(2, 11):</span><br><span class="line"> k = i + j</span><br><span class="line"> lst.append(k)</span><br><span class="line"> i = j</span><br><span class="line"> j = k</span><br><span class="line">print(lst) </span><br><span class="line"># [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]</span><br><span class="line"></span><br><span class="line"># 利用递归</span><br><span class="line">def recur_fibo(n):</span><br><span class="line"> if n <= 1:</span><br><span class="line"> return n</span><br><span class="line"> return recur_fibo(n - 1) + recur_fibo(n - 2)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">lst = list()</span><br><span class="line">for k in range(11):</span><br><span class="line"> lst.append(recur_fibo(k))</span><br><span class="line">print(lst) </span><br><span class="line"># [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]</span><br><span class="line">[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]</span><br><span class="line">[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]</span><br></pre></td></tr></table></figure><p>【例子】设置递归的层数，Python默认递归层数为 100</p><p>[22]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">import sys</span><br><span class="line"></span><br><span class="line">sys.setrecursionlimit(1000)</span><br></pre></td></tr></table></figure><h1 id="Lambda-表达式"><a href="#Lambda-表达式" class="headerlink" title="Lambda 表达式"></a>Lambda 表达式</h1><h2 id="匿名函数的定义"><a href="#匿名函数的定义" class="headerlink" title="匿名函数的定义"></a>匿名函数的定义</h2><p>在 Python 里有两类函数：</p><ul><li>第一类：用 <code>def</code> 关键词定义的正规函数</li><li>第二类：用 <code>lambda</code> 关键词定义的匿名函数</li></ul><p>Python 使用 <code>lambda</code> 关键词来创建匿名函数，而非<code>def</code>关键词，它没有函数名，其语法结构如下：</p><blockquote><p>lambda argument_list: expression</p></blockquote><ul><li><code>lambda</code> - 定义匿名函数的关键词。</li><li><code>argument_list</code> - 函数参数，它们可以是位置参数、默认参数、关键字参数，和正规函数里的参数类型一样。</li><li><code>:</code>- 冒号，在函数参数和表达式中间要加个冒号。</li><li><code>expression</code> - 只是一个表达式，输入函数参数，输出一些值。</li></ul><p>注意：</p><ul><li><code>expression</code> 中没有 return 语句，因为 lambda 不需要它来返回，表达式本身结果就是返回值。</li><li>匿名函数拥有自己的命名空间，且不能访问自己参数列表之外或全局命名空间里的参数。</li></ul><p>【例子】</p><p>[23]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br></pre></td><td class="code"><pre><span class="line">def sqr(x):</span><br><span class="line"> return x ** 2</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">print(sqr)</span><br><span class="line"># <function sqr at 0x000000BABD3A4400></span><br><span class="line"></span><br><span class="line">y = [sqr(x) for x in range(10)]</span><br><span class="line">print(y)</span><br><span class="line"># [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]</span><br><span class="line"></span><br><span class="line">lbd_sqr = lambda x: x ** 2</span><br><span class="line">print(lbd_sqr)</span><br><span class="line"># <function <lambda> at 0x000000BABB6AC1E0></span><br><span class="line"></span><br><span class="line">y = [lbd_sqr(x) for x in range(10)]</span><br><span class="line">print(y)</span><br><span class="line"># [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">sumary = lambda arg1, arg2: arg1 + arg2</span><br><span class="line">print(sumary(10, 20)) # 30</span><br><span class="line"></span><br><span class="line">func = lambda *args: sum(args)</span><br><span class="line">print(func(1, 2, 3, 4, 5)) # 15</span><br><span class="line"><function sqr at 0x00000220081D9E18></span><br><span class="line">[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]</span><br><span class="line"><function <lambda> at 0x00000220081FF400></span><br><span class="line">[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]</span><br><span class="line">30</span><br><span class="line">15</span><br></pre></td></tr></table></figure><h2 id="匿名函数的应用"><a href="#匿名函数的应用" class="headerlink" title="匿名函数的应用"></a>匿名函数的应用</h2><p>函数式编程 是指代码中每一块都是不可变的，都由纯函数的形式组成。这里的纯函数，是指函数本身相互独立、互不影响，对于相同的输入，总会有相同的输出，没有任何副作用。</p><p>【例子】非函数式编程</p><p>[24]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">def f(x):</span><br><span class="line"> for i in range(0, len(x)):</span><br><span class="line"> x[i] += 10</span><br><span class="line"> return x</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">x = [1, 2, 3]</span><br><span class="line">f(x)</span><br><span class="line">print(x)</span><br><span class="line"># [11, 12, 13]</span><br><span class="line">[11, 12, 13]</span><br></pre></td></tr></table></figure><p>【例子】函数式编程</p><p>[25]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">def f(x):</span><br><span class="line"> y = []</span><br><span class="line"> for item in x:</span><br><span class="line"> y.append(item + 10)</span><br><span class="line"> return y</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">x = [1, 2, 3]</span><br><span class="line">f(x)</span><br><span class="line">print(x)</span><br><span class="line"># [1, 2, 3]</span><br><span class="line">[1, 2, 3]</span><br></pre></td></tr></table></figure><p>匿名函数 常常应用于函数式编程的高阶函数 (high-order function)中，主要有两种形式：</p><ul><li>参数是函数 (filter, map)</li><li>返回值是函数 (closure)</li></ul><p>如，在 <code>filter</code>和<code>map</code>函数中的应用：</p><ul><li><code>filter(function, iterable)</code> 过滤序列，过滤掉不符合条件的元素，返回一个迭代器对象，如果要转换为列表，可以使用 <code>list()</code> 来转换。</li></ul><p>【例子】</p><p>[26]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">odd = lambda x: x % 2 == 1</span><br><span class="line">templist = filter(odd, [1, 2, 3, 4, 5, 6, 7, 8, 9])</span><br><span class="line">print(list(templist)) # [1, 3, 5, 7, 9]</span><br><span class="line">[1, 3, 5, 7, 9]</span><br></pre></td></tr></table></figure><ul><li><code>map(function, *iterables)</code> 根据提供的函数对指定序列做映射。</li></ul><p>【例子】</p><p>[27]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">m1 = map(lambda x: x ** 2, [1, 2, 3, 4, 5])</span><br><span class="line">print(list(m1)) </span><br><span class="line"># [1, 4, 9, 16, 25]</span><br><span class="line"></span><br><span class="line">m2 = map(lambda x, y: x + y, [1, 3, 5, 7, 9], [2, 4, 6, 8, 10])</span><br><span class="line">print(list(m2)) </span><br><span class="line"># [3, 7, 11, 15, 19]</span><br><span class="line">[1, 4, 9, 16, 25]</span><br><span class="line">[3, 7, 11, 15, 19]</span><br></pre></td></tr></table></figure><p>除了 Python 这些内置函数，我们也可以自己定义高阶函数。</p><p>【例子】</p><p>[28]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">def apply_to_list(fun, some_list):</span><br><span class="line"> return fun(some_list)</span><br><span class="line"></span><br><span class="line">lst = [1, 2, 3, 4, 5]</span><br><span class="line">print(apply_to_list(sum, lst))</span><br><span class="line"># 15</span><br><span class="line"></span><br><span class="line">print(apply_to_list(len, lst))</span><br><span class="line"># 5</span><br><span class="line"></span><br><span class="line">print(apply_to_list(lambda x: sum(x) / len(x), lst))</span><br><span class="line"># 3.0</span><br><span class="line">15</span><br><span class="line">5</span><br><span class="line">3.0</span><br></pre></td></tr></table></figure><h1 id="类与对象"><a href="#类与对象" class="headerlink" title="类与对象"></a>类与对象</h1><h2 id="对象-属性-方法"><a href="#对象-属性-方法" class="headerlink" title="对象 = 属性 + 方法"></a>对象 = 属性 + 方法</h2><p>对象是类的实例。换句话说，类主要定义对象的结构，然后我们以类为模板创建对象。类不但包含方法定义，而且还包含所有实例共享的数据。</p><ul><li>封装：信息隐蔽技术</li></ul><p>我们可以使用关键字 <code>class</code> 定义 Python 类，关键字后面紧跟类的名称、分号和类的实现。</p><p>【例子】</p><p>[31]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br></pre></td><td class="code"><pre><span class="line">class Turtle: # Python中的类名约定以大写字母开头</span><br><span class="line"> """关于类的一个简单例子"""</span><br><span class="line"> # 属性</span><br><span class="line"> color = 'green'</span><br><span class="line"> weight = 10</span><br><span class="line"> legs = 4</span><br><span class="line"> shell = True</span><br><span class="line"> mouth = '大嘴'</span><br><span class="line"></span><br><span class="line"> # 方法</span><br><span class="line"> def climb(self):</span><br><span class="line"> print('我正在很努力的向前爬...')</span><br><span class="line"></span><br><span class="line"> def run(self):</span><br><span class="line"> print('我正在飞快的向前跑...')</span><br><span class="line"></span><br><span class="line"> def bite(self):</span><br><span class="line"> print('咬死你咬死你!!')</span><br><span class="line"></span><br><span class="line"> def eat(self):</span><br><span class="line"> print('有得吃，真满足...')</span><br><span class="line"></span><br><span class="line"> def sleep(self):</span><br><span class="line"> print('困了，睡了，晚安，zzz')</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">tt = Turtle()</span><br><span class="line">print(tt)</span><br><span class="line"># <__main__.Turtle object at 0x0000007C32D67F98></span><br><span class="line"></span><br><span class="line">print(type(tt))</span><br><span class="line"># <class '__main__.Turtle'></span><br><span class="line"></span><br><span class="line">print(tt.__class__)</span><br><span class="line"># <class '__main__.Turtle'></span><br><span class="line"></span><br><span class="line">print(tt.__class__.__name__)</span><br><span class="line"># Turtle</span><br><span class="line"></span><br><span class="line">tt.climb()</span><br><span class="line"># 我正在很努力的向前爬...</span><br><span class="line"></span><br><span class="line">tt.run()</span><br><span class="line"># 我正在飞快的向前跑...</span><br><span class="line"></span><br><span class="line">tt.bite()</span><br><span class="line"># 咬死你咬死你!!</span><br><span class="line"></span><br><span class="line"># Python类也是对象。它们是type的实例</span><br><span class="line">print(type(Turtle))</span><br><span class="line"># <class 'type'></span><br><span class="line"><__main__.Turtle object at 0x000002200820E898></span><br><span class="line"><class '__main__.Turtle'></span><br><span class="line"><class '__main__.Turtle'></span><br><span class="line">Turtle</span><br><span class="line">我正在很努力的向前爬...</span><br><span class="line">我正在飞快的向前跑...</span><br><span class="line">咬死你咬死你!!</span><br><span class="line"><class 'type'></span><br></pre></td></tr></table></figure><ul><li>继承：子类自动共享父类之间数据和方法的机制</li></ul><p>【例子】</p><p>[32]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">class MyList(list):</span><br><span class="line"> pass</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">lst = MyList([1, 5, 2, 7, 8])</span><br><span class="line">lst.append(9)</span><br><span class="line">lst.sort()</span><br><span class="line">print(lst)</span><br><span class="line"></span><br><span class="line"># [1, 2, 5, 7, 8, 9]</span><br><span class="line">[1, 2, 5, 7, 8, 9]</span><br></pre></td></tr></table></figure><ul><li>多态：不同对象对同一方法响应不同的行动</li></ul><p>【例子】</p><p>[33]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line">class Animal:</span><br><span class="line"> def run(self):</span><br><span class="line"> raise AttributeError('子类必须实现这个方法')</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">class People(Animal):</span><br><span class="line"> def run(self):</span><br><span class="line"> print('人正在走')</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">class Pig(Animal):</span><br><span class="line"> def run(self):</span><br><span class="line"> print('pig is walking')</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">class Dog(Animal):</span><br><span class="line"> def run(self):</span><br><span class="line"> print('dog is running')</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">def func(animal):</span><br><span class="line"> animal.run()</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">func(Pig())</span><br><span class="line"># pig is walking</span><br><span class="line">pig is walking</span><br></pre></td></tr></table></figure><hr><h2 id="self-是什么？"><a href="#self-是什么？" class="headerlink" title="self 是什么？"></a>self 是什么？</h2><p>Python 的 <code>self</code> 相当于 C++ 的 <code>this</code> 指针。</p><p>【例子】</p><p>[34]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">class Test:</span><br><span class="line"> def prt(self):</span><br><span class="line"> print(self)</span><br><span class="line"> print(self.__class__)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">t = Test()</span><br><span class="line">t.prt()</span><br><span class="line"># <__main__.Test object at 0x000000BC5A351208></span><br><span class="line"># <class '__main__.Test'></span><br><span class="line"><__main__.Test object at 0x000002200820EA20></span><br><span class="line"><class '__main__.Test'></span><br></pre></td></tr></table></figure><p>类的方法与普通的函数只有一个特别的区别 —— 它们必须有一个额外的第一个参数名称（对应于该实例，即该对象本身），按照惯例它的名称是 <code>self</code>。在调用方法时，我们无需明确提供与参数 <code>self</code> 相对应的参数。</p><p>【例子】</p><p>[35]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line">class Ball:</span><br><span class="line"> def setName(self, name):</span><br><span class="line"> self.name = name</span><br><span class="line"></span><br><span class="line"> def kick(self):</span><br><span class="line"> print("我叫%s,该死的，谁踢我..." % self.name)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">a = Ball()</span><br><span class="line">a.setName("球A")</span><br><span class="line">b = Ball()</span><br><span class="line">b.setName("球B")</span><br><span class="line">c = Ball()</span><br><span class="line">c.setName("球C")</span><br><span class="line">a.kick()</span><br><span class="line"># 我叫球A,该死的，谁踢我...</span><br><span class="line">b.kick()</span><br><span class="line"># 我叫球B,该死的，谁踢我...</span><br><span class="line">我叫球A,该死的，谁踢我...</span><br><span class="line">我叫球B,该死的，谁踢我...</span><br></pre></td></tr></table></figure><hr><h2 id="Python-的魔法方法"><a href="#Python-的魔法方法" class="headerlink" title="Python 的魔法方法"></a>Python 的魔法方法</h2><p>据说，Python 的对象天生拥有一些神奇的方法，它们是面向对象的 Python 的一切…</p><p>它们是可以给你的类增加魔力的特殊方法…</p><p>如果你的对象实现了这些方法中的某一个，那么这个方法就会在特殊的情况下被 Python 所调用，而这一切都是自动发生的…</p><p>类有一个名为<code>__init__(self[, param1, param2...])</code>的魔法方法，该方法在类实例化时会自动调用。</p><p>【例子】</p><p>[36]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">class Ball:</span><br><span class="line"> def __init__(self, name):</span><br><span class="line"> self.name = name</span><br><span class="line"></span><br><span class="line"> def kick(self):</span><br><span class="line"> print("我叫%s,该死的，谁踢我..." % self.name)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">a = Ball("球A")</span><br><span class="line">b = Ball("球B")</span><br><span class="line">c = Ball("球C")</span><br><span class="line">a.kick()</span><br><span class="line"># 我叫球A,该死的，谁踢我...</span><br><span class="line">b.kick()</span><br><span class="line"># 我叫球B,该死的，谁踢我...</span><br><span class="line">我叫球A,该死的，谁踢我...</span><br><span class="line">我叫球B,该死的，谁踢我...</span><br></pre></td></tr></table></figure><hr><h2 id="公有和私有"><a href="#公有和私有" class="headerlink" title="公有和私有"></a>公有和私有</h2><p>在 Python 中定义私有变量只需要在变量名或函数名前加上“__”两个下划线，那么这个函数或变量就会为私有的了。</p><p>【例子】类的私有属性实例</p><p>[38]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line">class JustCounter:</span><br><span class="line"> __secretCount = 0 # 私有变量</span><br><span class="line"> publicCount = 0 # 公开变量</span><br><span class="line"></span><br><span class="line"> def count(self):</span><br><span class="line"> self.__secretCount += 1</span><br><span class="line"> self.publicCount += 1</span><br><span class="line"> print(self.__secretCount)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">counter = JustCounter()</span><br><span class="line">counter.count() # 1</span><br><span class="line">counter.count() # 2</span><br><span class="line">print(counter.publicCount) # 2</span><br><span class="line"></span><br><span class="line"># Python的私有为伪私有</span><br><span class="line">print(counter._JustCounter__secretCount) # 2 </span><br><span class="line">print(counter.__secretCount) </span><br><span class="line"># AttributeError: 'JustCounter' object has no attribute '__secretCount'</span><br><span class="line">1</span><br><span class="line">2</span><br><span class="line">2</span><br><span class="line">2</span><br></pre></td></tr></table></figure><p>【例子】类的私有方法实例</p><p>[40]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br></pre></td><td class="code"><pre><span class="line">class Site:</span><br><span class="line"> def __init__(self, name, url):</span><br><span class="line"> self.name = name # public</span><br><span class="line"> self.__url = url # private</span><br><span class="line"></span><br><span class="line"> def who(self):</span><br><span class="line"> print('name : ', self.name)</span><br><span class="line"> print('url : ', self.__url)</span><br><span class="line"></span><br><span class="line"> def __foo(self): # 私有方法</span><br><span class="line"> print('这是私有方法')</span><br><span class="line"></span><br><span class="line"> def foo(self): # 公共方法</span><br><span class="line"> print('这是公共方法')</span><br><span class="line"> self.__foo()</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">x = Site('老马的程序人生', 'https://blog.csdn.net/LSGO_MYP')</span><br><span class="line">x.who()</span><br><span class="line"># name : 老马的程序人生</span><br><span class="line"># url : https://blog.csdn.net/LSGO_MYP</span><br><span class="line"></span><br><span class="line">x.foo()</span><br><span class="line"># 这是公共方法</span><br><span class="line"># 这是私有方法</span><br><span class="line"></span><br><span class="line">x.__foo()</span><br><span class="line"># AttributeError: 'Site' object has no attribute '__foo'</span><br><span class="line">name : 老马的程序人生</span><br><span class="line">url : https://blog.csdn.net/LSGO_MYP</span><br><span class="line">这是公共方法</span><br><span class="line">这是私有方法</span><br></pre></td></tr></table></figure><hr><h2 id="继承"><a href="#继承" class="headerlink" title="继承"></a>继承</h2><p>Python 同样支持类的继承，派生类的定义如下所示：</p><blockquote><p>class DerivedClassName(BaseClassName):<br> statement-1<br> .<br> .<br> .<br> statement-N</p></blockquote><p><code>BaseClassName</code>（基类名）必须与派生类定义在一个作用域内。除了类，还可以用表达式，基类定义在另一个模块中时这一点非常有用：</p><blockquote><p>class DerivedClassName(modname.BaseClassName):<br> statement-1<br> .<br> .<br> .<br> statement-N</p></blockquote><p>【例子】如果子类中定义与父类同名的方法或属性，则会自动覆盖父类对应的方法或属性。</p><p>[41]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br></pre></td><td class="code"><pre><span class="line"># 类定义</span><br><span class="line">class people:</span><br><span class="line"> # 定义基本属性</span><br><span class="line"> name = ''</span><br><span class="line"> age = 0</span><br><span class="line"> # 定义私有属性,私有属性在类外部无法直接进行访问</span><br><span class="line"> __weight = 0</span><br><span class="line"></span><br><span class="line"> # 定义构造方法</span><br><span class="line"> def __init__(self, n, a, w):</span><br><span class="line"> self.name = n</span><br><span class="line"> self.age = a</span><br><span class="line"> self.__weight = w</span><br><span class="line"></span><br><span class="line"> def speak(self):</span><br><span class="line"> print("%s 说: 我 %d 岁。" % (self.name, self.age))</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"># 单继承示例</span><br><span class="line">class student(people):</span><br><span class="line"> grade = ''</span><br><span class="line"></span><br><span class="line"> def __init__(self, n, a, w, g):</span><br><span class="line"> # 调用父类的构函</span><br><span class="line"> people.__init__(self, n, a, w)</span><br><span class="line"> self.grade = g</span><br><span class="line"></span><br><span class="line"> # 覆写父类的方法</span><br><span class="line"> def speak(self):</span><br><span class="line"> print("%s 说: 我 %d 岁了，我在读 %d 年级" % (self.name, self.age, self.grade))</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">s = student('小马的程序人生', 10, 60, 3)</span><br><span class="line">s.speak()</span><br><span class="line"># 小马的程序人生 说: 我 10 岁了，我在读 3 年级</span><br><span class="line">小马的程序人生 说: 我 10 岁了，我在读 3 年级</span><br></pre></td></tr></table></figure><p>注意：如果上面的程序去掉：<code>people.__init__(self, n, a, w)</code>，则输出：<code>说: 我 0 岁了，我在读 3 年级</code>，因为子类的构造方法把父类的构造方法覆盖了。</p><p>【例子】</p><p>[43]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br></pre></td><td class="code"><pre><span class="line">import random</span><br><span class="line"></span><br><span class="line">class Fish:</span><br><span class="line"> def __init__(self):</span><br><span class="line"> self.x = random.randint(0, 10)</span><br><span class="line"> self.y = random.randint(0, 10)</span><br><span class="line"></span><br><span class="line"> def move(self):</span><br><span class="line"> self.x -= 1</span><br><span class="line"> print("我的位置", self.x, self.y)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">class GoldFish(Fish): # 金鱼</span><br><span class="line"> pass</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">class Carp(Fish): # 鲤鱼</span><br><span class="line"> pass</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">class Salmon(Fish): # 三文鱼</span><br><span class="line"> pass</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">class Shark(Fish): # 鲨鱼</span><br><span class="line"> def __init__(self):</span><br><span class="line"> self.hungry = True</span><br><span class="line"></span><br><span class="line"> def eat(self):</span><br><span class="line"> if self.hungry:</span><br><span class="line"> print("吃货的梦想就是天天有得吃！")</span><br><span class="line"> self.hungry = False</span><br><span class="line"> else:</span><br><span class="line"> print("太撑了，吃不下了！")</span><br><span class="line"> self.hungry = True</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">g = GoldFish()</span><br><span class="line">g.move() # 我的位置 9 4</span><br><span class="line">s = Shark()</span><br><span class="line">s.eat() # 吃货的梦想就是天天有得吃！</span><br><span class="line">s.move() </span><br><span class="line"># AttributeError: 'Shark' object has no attribute 'x'</span><br><span class="line">我的位置 3 8</span><br><span class="line">吃货的梦想就是天天有得吃！</span><br></pre></td></tr></table></figure><p>解决该问题可用以下两种方式：</p><ul><li>调用未绑定的父类方法<code>Fish.__init__(self)</code></li></ul><p>[44]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">class Shark(Fish): # 鲨鱼</span><br><span class="line"> def __init__(self):</span><br><span class="line"> Fish.__init__(self)</span><br><span class="line"> self.hungry = True</span><br><span class="line"></span><br><span class="line"> def eat(self):</span><br><span class="line"> if self.hungry:</span><br><span class="line"> print("吃货的梦想就是天天有得吃！")</span><br><span class="line"> self.hungry = False</span><br><span class="line"> else:</span><br><span class="line"> print("太撑了，吃不下了！")</span><br><span class="line"> self.hungry = True</span><br></pre></td></tr></table></figure><ul><li>使用super函数<code>super().__init__()</code></li></ul><p>[45]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">class Shark(Fish): # 鲨鱼</span><br><span class="line"> def __init__(self):</span><br><span class="line"> super().__init__()</span><br><span class="line"> self.hungry = True</span><br><span class="line"></span><br><span class="line"> def eat(self):</span><br><span class="line"> if self.hungry:</span><br><span class="line"> print("吃货的梦想就是天天有得吃！")</span><br><span class="line"> self.hungry = False</span><br><span class="line"> else:</span><br><span class="line"> print("太撑了，吃不下了！")</span><br><span class="line"> self.hungry = True</span><br></pre></td></tr></table></figure><p>Python 虽然支持多继承的形式，但我们一般不使用多继承，因为容易引起混乱。</p><blockquote><p>class DerivedClassName(Base1, Base2, Base3):<br> statement-1<br> .<br> .<br> .<br> statement-N</p></blockquote><p>需要注意圆括号中父类的顺序，若是父类中有相同的方法名，而在子类使用时未指定，Python 从左至右搜索，即方法在子类中未找到时，从左到右查找父类中是否包含方法。</p><p>【例子】</p><p>[47]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br></pre></td><td class="code"><pre><span class="line"># 类定义</span><br><span class="line">class People:</span><br><span class="line"> # 定义基本属性</span><br><span class="line"> name = ''</span><br><span class="line"> age = 0</span><br><span class="line"> # 定义私有属性,私有属性在类外部无法直接进行访问</span><br><span class="line"> __weight = 0</span><br><span class="line"></span><br><span class="line"> # 定义构造方法</span><br><span class="line"> def __init__(self, n, a, w):</span><br><span class="line"> self.name = n</span><br><span class="line"> self.age = a</span><br><span class="line"> self.__weight = w</span><br><span class="line"></span><br><span class="line"> def speak(self):</span><br><span class="line"> print("%s 说: 我 %d 岁。" % (self.name, self.age))</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"># 单继承示例</span><br><span class="line">class Student(People):</span><br><span class="line"> grade = ''</span><br><span class="line"></span><br><span class="line"> def __init__(self, n, a, w, g):</span><br><span class="line"> # 调用父类的构函</span><br><span class="line"> People.__init__(self, n, a, w)</span><br><span class="line"> self.grade = g</span><br><span class="line"></span><br><span class="line"> # 覆写父类的方法</span><br><span class="line"> def speak(self):</span><br><span class="line"> print("%s 说: 我 %d 岁了，我在读 %d 年级" % (self.name, self.age, self.grade))</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"># 另一个类，多重继承之前的准备</span><br><span class="line">class Speaker:</span><br><span class="line"> topic = ''</span><br><span class="line"> name = ''</span><br><span class="line"></span><br><span class="line"> def __init__(self, n, t):</span><br><span class="line"> self.name = n</span><br><span class="line"> self.topic = t</span><br><span class="line"></span><br><span class="line"> def speak(self):</span><br><span class="line"> print("我叫 %s，我是一个演说家，我演讲的主题是 %s" % (self.name, self.topic))</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"># 多重继承</span><br><span class="line">class Sample01(Speaker, Student):</span><br><span class="line"> a = ''</span><br><span class="line"></span><br><span class="line"> def __init__(self, n, a, w, g, t):</span><br><span class="line"> Student.__init__(self, n, a, w, g)</span><br><span class="line"> Speaker.__init__(self, n, t)</span><br><span class="line"></span><br><span class="line"># 方法名同，默认调用的是在括号中排前地父类的方法</span><br><span class="line">test = Sample01("Tim", 25, 80, 4, "Python")</span><br><span class="line">test.speak() </span><br><span class="line"># 我叫 Tim，我是一个演说家，我演讲的主题是 Python</span><br><span class="line"></span><br><span class="line">class Sample02(Student, Speaker):</span><br><span class="line"> a = ''</span><br><span class="line"></span><br><span class="line"> def __init__(self, n, a, w, g, t):</span><br><span class="line"> Student.__init__(self, n, a, w, g)</span><br><span class="line"> Speaker.__init__(self, n, t)</span><br><span class="line"></span><br><span class="line"># 方法名同，默认调用的是在括号中排前地父类的方法</span><br><span class="line">test = Sample02("Tim", 25, 80, 4, "Python")</span><br><span class="line">test.speak() </span><br><span class="line"># Tim 说: 我 25 岁了，我在读 4 年级</span><br><span class="line">我叫 Tim，我是一个演说家，我演讲的主题是 Python</span><br><span class="line">Tim 说: 我 25 岁了，我在读 4 年级</span><br></pre></td></tr></table></figure><h2 id="组合"><a href="#组合" class="headerlink" title="组合"></a>组合</h2><p>【例子】</p><p>[48]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line">class Turtle:</span><br><span class="line"> def __init__(self, x):</span><br><span class="line"> self.num = x</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">class Fish:</span><br><span class="line"> def __init__(self, x):</span><br><span class="line"> self.num = x</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">class Pool:</span><br><span class="line"> def __init__(self, x, y):</span><br><span class="line"> self.turtle = Turtle(x)</span><br><span class="line"> self.fish = Fish(y)</span><br><span class="line"></span><br><span class="line"> def print_num(self):</span><br><span class="line"> print("水池里面有乌龟%s只，小鱼%s条" % (self.turtle.num, self.fish.num))</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">p = Pool(2, 3)</span><br><span class="line">p.print_num()</span><br><span class="line"># 水池里面有乌龟2只，小鱼3条</span><br><span class="line">水池里面有乌龟2只，小鱼3条</span><br></pre></td></tr></table></figure><h2 id="类、类对象和实例对象"><a href="#类、类对象和实例对象" class="headerlink" title="类、类对象和实例对象"></a>类、类对象和实例对象</h2><p><img src="https://img-blog.csdnimg.cn/20191007090316462.png" alt="类对象和实例对象"></p><p>类对象：创建一个类，其实也是一个对象也在内存开辟了一块空间，称为类对象，类对象只有一个。</p><blockquote><p>class A(object):<br> pass</p></blockquote><p>实例对象：就是通过实例化类创建的对象，称为实例对象，实例对象可以有多个。</p><p>【例子】</p><p>[49]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">class A(object):</span><br><span class="line"> pass</span><br><span class="line"></span><br><span class="line"># 实例化对象 a、b、c都属于实例对象。</span><br><span class="line">a = A()</span><br><span class="line">b = A()</span><br><span class="line">c = A()</span><br></pre></td></tr></table></figure><p>类属性：类里面方法外面定义的变量称为类属性。类属性所属于类对象并且多个实例对象之间共享同一个类属性，说白了就是类属性所有的通过该类实例化的对象都能共享。</p><p>【例子】</p><p>[3]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">class A():</span><br><span class="line"> a = 0 #类属性</span><br><span class="line"> def __init__(self, xx):</span><br><span class="line"> A.a = xx #使用类属性可以通过 （类名.类属性）调用。</span><br></pre></td></tr></table></figure><p>实例属性：实例属性和具体的某个实例对象有关系，并且一个实例对象和另外一个实例对象是不共享属性的，说白了实例属性只能在自己的对象里面使用，其他的对象不能直接使用，因为<code>self</code>是谁调用，它的值就属于该对象。</p><p>【例子】</p><p>[56]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br></pre></td><td class="code"><pre><span class="line"># 创建类对象</span><br><span class="line">class Test(object):</span><br><span class="line"> class_attr = 100 # 类属性</span><br><span class="line"></span><br><span class="line"> def __init__(self):</span><br><span class="line"> self.sl_attr = 100 # 实例属性</span><br><span class="line"></span><br><span class="line"> def func(self):</span><br><span class="line"> print('类对象.类属性的值:', Test.class_attr) # 调用类属性</span><br><span class="line"> print('self.类属性的值', self.class_attr) # 相当于把类属性 变成实例属性</span><br><span class="line"> print('self.实例属性的值', self.sl_attr) # 调用实例属性</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">a = Test()</span><br><span class="line">a.func()</span><br><span class="line"></span><br><span class="line"># 类对象.类属性的值: 100</span><br><span class="line"># self.类属性的值 100</span><br><span class="line"># self.实例属性的值 100</span><br><span class="line"></span><br><span class="line">b = Test()</span><br><span class="line">b.func()</span><br><span class="line"></span><br><span class="line"># 类对象.类属性的值: 100</span><br><span class="line"># self.类属性的值 100</span><br><span class="line"># self.实例属性的值 100</span><br><span class="line"></span><br><span class="line">a.class_attr = 200</span><br><span class="line">a.sl_attr = 200</span><br><span class="line">a.func()</span><br><span class="line"></span><br><span class="line"># 类对象.类属性的值: 100</span><br><span class="line"># self.类属性的值 200</span><br><span class="line"># self.实例属性的值 200</span><br><span class="line"></span><br><span class="line">b.func()</span><br><span class="line"></span><br><span class="line"># 类对象.类属性的值: 100</span><br><span class="line"># self.类属性的值 100</span><br><span class="line"># self.实例属性的值 100</span><br><span class="line"></span><br><span class="line">Test.class_attr = 300</span><br><span class="line">a.func()</span><br><span class="line"></span><br><span class="line"># 类对象.类属性的值: 300</span><br><span class="line"># self.类属性的值 200</span><br><span class="line"># self.实例属性的值 200</span><br><span class="line"></span><br><span class="line">b.func()</span><br><span class="line"># 类对象.类属性的值: 300</span><br><span class="line"># self.类属性的值 300</span><br><span class="line"># self.实例属性的值 100</span><br><span class="line">类对象.类属性的值: 100</span><br><span class="line">self.类属性的值 100</span><br><span class="line">self.实例属性的值 100</span><br><span class="line">类对象.类属性的值: 100</span><br><span class="line">self.类属性的值 100</span><br><span class="line">self.实例属性的值 100</span><br><span class="line">类对象.类属性的值: 100</span><br><span class="line">self.类属性的值 200</span><br><span class="line">self.实例属性的值 200</span><br><span class="line">类对象.类属性的值: 100</span><br><span class="line">self.类属性的值 100</span><br><span class="line">self.实例属性的值 100</span><br><span class="line">类对象.类属性的值: 300</span><br><span class="line">self.类属性的值 200</span><br><span class="line">self.实例属性的值 200</span><br><span class="line">类对象.类属性的值: 300</span><br><span class="line">self.类属性的值 300</span><br><span class="line">self.实例属性的值 100</span><br></pre></td></tr></table></figure><p>注意：属性与方法名相同，属性会覆盖方法。</p><p>【例子】</p><p>[57]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">class A:</span><br><span class="line"> def x(self):</span><br><span class="line"> print('x_man')</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">aa = A()</span><br><span class="line">aa.x() # x_man</span><br><span class="line">aa.x = 1</span><br><span class="line">print(aa.x) # 1</span><br><span class="line">aa.x()</span><br><span class="line"># TypeError: 'int' object is not callable</span><br><span class="line">x_man</span><br><span class="line">1</span><br></pre></td></tr></table></figure><h2 id="什么是绑定？"><a href="#什么是绑定？" class="headerlink" title="什么是绑定？"></a>什么是绑定？</h2><p>Python 严格要求方法需要有实例才能被调用，这种限制其实就是 Python 所谓的绑定概念。</p><p>Python 对象的数据属性通常存储在名为<code>.__ dict__</code>的字典中，我们可以直接访问<code>__dict__</code>，或利用 Python 的内置函数<code>vars()</code>获取<code>.__ dict__</code>。</p><p>【例子】</p><p>[58]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><span class="line">class CC:</span><br><span class="line"> def setXY(self, x, y):</span><br><span class="line"> self.x = x</span><br><span class="line"> self.y = y</span><br><span class="line"></span><br><span class="line"> def printXY(self):</span><br><span class="line"> print(self.x, self.y)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">dd = CC()</span><br><span class="line">print(dd.__dict__)</span><br><span class="line"># {}</span><br><span class="line"></span><br><span class="line">print(vars(dd))</span><br><span class="line"># {}</span><br><span class="line"></span><br><span class="line">print(CC.__dict__)</span><br><span class="line"># {'__module__': '__main__', 'setXY': <function CC.setXY at 0x000000C3473DA048>, 'printXY': <function CC.printXY at 0x000000C3473C4F28>, '__dict__': <attribute '__dict__' of 'CC' objects>, '__weakref__': <attribute '__weakref__' of 'CC' objects>, '__doc__': None}</span><br><span class="line"></span><br><span class="line">dd.setXY(4, 5)</span><br><span class="line">print(dd.__dict__)</span><br><span class="line"># {'x': 4, 'y': 5}</span><br><span class="line"></span><br><span class="line">print(vars(CC))</span><br><span class="line"># {'__module__': '__main__', 'setXY': <function CC.setXY at 0x000000632CA9B048>, 'printXY': <function CC.printXY at 0x000000632CA83048>, '__dict__': <attribute '__dict__' of 'CC' objects>, '__weakref__': <attribute '__weakref__' of 'CC' objects>, '__doc__': None}</span><br><span class="line"></span><br><span class="line">print(CC.__dict__)</span><br><span class="line"># {'__module__': '__main__', 'setXY': <function CC.setXY at 0x000000632CA9B048>, 'printXY': <function CC.printXY at 0x000000632CA83048>, '__dict__': <attribute '__dict__' of 'CC' objects>, '__weakref__': <attribute '__weakref__' of 'CC' objects>, '__doc__': None}</span><br><span class="line">{}</span><br><span class="line">{}</span><br><span class="line">{'__module__': '__main__', 'setXY': <function CC.setXY at 0x000002200822BD08>, 'printXY': <function CC.printXY at 0x000002200822BF28>, '__dict__': <attribute '__dict__' of 'CC' objects>, '__weakref__': <attribute '__weakref__' of 'CC' objects>, '__doc__': None}</span><br><span class="line">{'x': 4, 'y': 5}</span><br><span class="line">{'__module__': '__main__', 'setXY': <function CC.setXY at 0x000002200822BD08>, 'printXY': <function CC.printXY at 0x000002200822BF28>, '__dict__': <attribute '__dict__' of 'CC' objects>, '__weakref__': <attribute '__weakref__' of 'CC' objects>, '__doc__': None}</span><br><span class="line">{'__module__': '__main__', 'setXY': <function CC.setXY at 0x000002200822BD08>, 'printXY': <function CC.printXY at 0x000002200822BF28>, '__dict__': <attribute '__dict__' of 'CC' objects>, '__weakref__': <attribute '__weakref__' of 'CC' objects>, '__doc__': None}</span><br></pre></td></tr></table></figure><h2 id="一些相关的内置函数（BIF）"><a href="#一些相关的内置函数（BIF）" class="headerlink" title="一些相关的内置函数（BIF）"></a>一些相关的内置函数（BIF）</h2><ul><li><code>issubclass(class, classinfo)</code> 方法用于判断参数 class 是否是类型参数 classinfo 的子类。</li><li>一个类被认为是其自身的子类。</li><li><code>classinfo</code>可以是类对象的元组，只要class是其中任何一个候选类的子类，则返回<code>True</code>。</li></ul><p>【例子】</p><p>[59]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line">class A:</span><br><span class="line"> pass</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">class B(A):</span><br><span class="line"> pass</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">print(issubclass(B, A)) # True</span><br><span class="line">print(issubclass(B, B)) # True</span><br><span class="line">print(issubclass(A, B)) # False</span><br><span class="line">print(issubclass(B, object)) # True</span><br><span class="line">True</span><br><span class="line">True</span><br><span class="line">False</span><br><span class="line">True</span><br></pre></td></tr></table></figure><ul><li><code>isinstance(object, classinfo)</code> 方法用于判断一个对象是否是一个已知的类型，类似<code>type()</code>。</li><li><code>type()</code>不会认为子类是一种父类类型，不考虑继承关系。</li><li><code>isinstance()</code>会认为子类是一种父类类型，考虑继承关系。</li><li>如果第一个参数不是对象，则永远返回<code>False</code>。</li><li>如果第二个参数不是类或者由类对象组成的元组，会抛出一个<code>TypeError</code>异常。</li></ul><p>【例子】</p><p>[60]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line">a = 2</span><br><span class="line">print(isinstance(a, int)) # True</span><br><span class="line">print(isinstance(a, str)) # False</span><br><span class="line">print(isinstance(a, (str, int, list))) # True</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">class A:</span><br><span class="line"> pass</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">class B(A):</span><br><span class="line"> pass</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">print(isinstance(A(), A)) # True</span><br><span class="line">print(type(A()) == A) # True</span><br><span class="line">print(isinstance(B(), A)) # True</span><br><span class="line">print(type(B()) == A) # False</span><br><span class="line">True</span><br><span class="line">False</span><br><span class="line">True</span><br><span class="line">True</span><br><span class="line">True</span><br><span class="line">True</span><br><span class="line">False</span><br></pre></td></tr></table></figure><ul><li><code>hasattr(object, name)</code>用于判断对象是否包含对应的属性。</li></ul><p>【例子】</p><p>[61]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">class Coordinate:</span><br><span class="line"> x = 10</span><br><span class="line"> y = -5</span><br><span class="line"> z = 0</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">point1 = Coordinate()</span><br><span class="line">print(hasattr(point1, 'x')) # True</span><br><span class="line">print(hasattr(point1, 'y')) # True</span><br><span class="line">print(hasattr(point1, 'z')) # True</span><br><span class="line">print(hasattr(point1, 'no')) # False</span><br><span class="line">True</span><br><span class="line">True</span><br><span class="line">True</span><br><span class="line">False</span><br></pre></td></tr></table></figure><ul><li><code>getattr(object, name[, default])</code>用于返回一个对象属性值。</li></ul><p>【例子】</p><p>[63]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">class A(object):</span><br><span class="line"> bar = 1</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">a = A()</span><br><span class="line">print(getattr(a, 'bar')) # 1</span><br><span class="line">print(getattr(a, 'bar2', 3)) # 3</span><br><span class="line">print(getattr(a, 'bar2'))</span><br><span class="line"># AttributeError: 'A' object has no attribute 'bar2'</span><br><span class="line">1</span><br><span class="line">3</span><br></pre></td></tr></table></figure><p>【例子】这个例子很酷！</p><p>[64]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">class A(object):</span><br><span class="line"> def set(self, a, b):</span><br><span class="line"> x = a</span><br><span class="line"> a = b</span><br><span class="line"> b = x</span><br><span class="line"> print(a, b)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">a = A()</span><br><span class="line">c = getattr(a, 'set')</span><br><span class="line">c(a='1', b='2') # 2 1</span><br><span class="line"></span><br><span class="line">2 1</span><br></pre></td></tr></table></figure><ul><li><code>setattr(object, name, value)</code>对应函数 <code>getattr()</code>，用于设置属性值，该属性不一定是存在的。</li></ul><p>【例子】</p><p>[65]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">class A(object):</span><br><span class="line"> bar = 1</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">a = A()</span><br><span class="line">print(getattr(a, 'bar')) # 1</span><br><span class="line">setattr(a, 'bar', 5)</span><br><span class="line">print(a.bar) # 5</span><br><span class="line">setattr(a, "age", 28)</span><br><span class="line">print(a.age) # 28</span><br><span class="line">1</span><br><span class="line">5</span><br><span class="line">28</span><br></pre></td></tr></table></figure><ul><li><code>delattr(object, name)</code>用于删除属性。</li></ul><p>【例子】</p><p>[66]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line">class Coordinate:</span><br><span class="line"> x = 10</span><br><span class="line"> y = -5</span><br><span class="line"> z = 0</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">point1 = Coordinate()</span><br><span class="line"></span><br><span class="line">print('x = ', point1.x) # x = 10</span><br><span class="line">print('y = ', point1.y) # y = -5</span><br><span class="line">print('z = ', point1.z) # z = 0</span><br><span class="line"></span><br><span class="line">delattr(Coordinate, 'z')</span><br><span class="line"></span><br><span class="line">print('--删除 z 属性后--') # --删除 z 属性后--</span><br><span class="line">print('x = ', point1.x) # x = 10</span><br><span class="line">print('y = ', point1.y) # y = -5</span><br><span class="line"></span><br><span class="line"># 触发错误</span><br><span class="line">print('z = ', point1.z)</span><br><span class="line"># AttributeError: 'Coordinate' object has no attribute 'z'</span><br><span class="line">x = 10</span><br><span class="line">y = -5</span><br><span class="line">z = 0</span><br><span class="line">--删除 z 属性后--</span><br><span class="line">x = 10</span><br><span class="line">y = -5</span><br></pre></td></tr></table></figure><ul><li><pre><code>class property([fget[, fset[, fdel[, doc]]]])<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"> 用于在新式类中返回属性值。</span><br><span class="line"></span><br><span class="line"> - `fget` -- 获取属性值的函数</span><br><span class="line"> - `fset` -- 设置属性值的函数</span><br><span class="line"> - `fdel` -- 删除属性值函数</span><br><span class="line"> - `doc` -- 属性描述信息</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[67]:</span><br></pre></td></tr></table></figure>class C(object): def __init__(self): self.__x = None def getx(self): return self.__x def setx(self, value): self.__x = value def delx(self): del self.__x x = property(getx, setx, delx, "I'm the 'x' property.")</code></pre></li></ul><p>cc = C()<br>cc.x = 2<br>print(cc.x) # 2</p><p>del cc.x<br>print(cc.x)</p><h1 id="AttributeError-‘C’-object-has-no-attribute-‘-C-x’"><a href="#AttributeError-‘C’-object-has-no-attribute-‘-C-x’" class="headerlink" title="AttributeError: ‘C’ object has no attribute ‘_C__x’"></a>AttributeError: ‘C’ object has no attribute ‘_C__x’</h1><p>2</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"># 魔法方法</span><br><span class="line"></span><br><span class="line">魔法方法总是被双下划线包围，例如`__init__`。</span><br><span class="line"></span><br><span class="line">魔法方法是面向对象的 Python 的一切，如果你不知道魔法方法，说明你还没能意识到面向对象的 Python 的强大。</span><br><span class="line"></span><br><span class="line">魔法方法的“魔力”体现在它们总能够在适当的时候被自动调用。</span><br><span class="line"></span><br><span class="line">魔法方法的第一个参数应为`cls`（类方法） 或者`self`（实例方法）。</span><br><span class="line"></span><br><span class="line">- `cls`：代表一个类的名称</span><br><span class="line">- `self`：代表一个实例对象的名称</span><br><span class="line"></span><br><span class="line">## 基本的魔法方法</span><br><span class="line"></span><br><span class="line">- `__init__(self[, ...])` 构造器，当一个实例被创建的时候调用的初始化方法</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[68]:</span><br></pre></td></tr></table></figure><p>class Rectangle:<br> def <strong>init</strong>(self, x, y):<br> self.x = x<br> self.y = y</p><pre><code>def getPeri(self): return (self.x + self.y) * 2def getArea(self): return self.x * self.y</code></pre><p>rect = Rectangle(4, 5)<br>print(rect.getPeri()) # 18<br>print(rect.getArea()) # 20<br>18<br>20</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">-</span><br></pre></td></tr></table></figure><p> <strong>new</strong>(cls[, …])<br> <figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line">在一个对象实例化的时候所调用的第一个方法，在调用</span><br></pre></td></tr></table></figure><br> <strong>init</strong><br> <figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">初始化前，先调用</span><br></pre></td></tr></table></figure><br> <strong>new</strong><br> <figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"> 。</span><br><span class="line"></span><br><span class="line"> - `__new__`至少要有一个参数`cls`，代表要实例化的类，此参数在实例化时由 Python 解释器自动提供，后面的参数直接传递给`__init__`。</span><br><span class="line"> - `__new__`对当前类进行了实例化，并将实例返回，传给`__init__`的`self`。但是，执行了`__new__`，并不一定会进入`__init__`，只有`__new__`返回了，当前类`cls`的实例，当前类的`__init__`才会进入。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[69]:</span><br></pre></td></tr></table></figure><br>class A(object):<br> def <strong>init</strong>(self, value):<br> print(“into A <strong>init</strong>“)<br> self.value = value</p><pre><code>def __new__(cls, *args, **kwargs): print("into A __new__") print(cls) return object.__new__(cls)</code></pre><p>class B(A):<br> def <strong>init</strong>(self, value):<br> print(“into B <strong>init</strong>“)<br> self.value = value</p><pre><code>def __new__(cls, *args, **kwargs): print("into B __new__") print(cls) return super().__new__(cls, *args, **kwargs)</code></pre><p>b = B(10)</p><h1 id="结果："><a href="#结果：" class="headerlink" title="结果："></a>结果：</h1><h1 id="into-B-new"><a href="#into-B-new" class="headerlink" title="into B new"></a>into B <strong>new</strong></h1><h1 id="lt-class-‘main-B’-gt"><a href="#lt-class-‘main-B’-gt" class="headerlink" title="<class ‘main.B’>"></a><class ‘<strong>main</strong>.B’></h1><h1 id="into-A-new"><a href="#into-A-new" class="headerlink" title="into A new"></a>into A <strong>new</strong></h1><h1 id="lt-class-‘main-B’-gt-1"><a href="#lt-class-‘main-B’-gt-1" class="headerlink" title="<class ‘main.B’>"></a><class ‘<strong>main</strong>.B’></h1><h1 id="into-B-init"><a href="#into-B-init" class="headerlink" title="into B init"></a>into B <strong>init</strong></h1><p>class A(object):<br> def <strong>init</strong>(self, value):<br> print(“into A <strong>init</strong>“)<br> self.value = value</p><pre><code>def __new__(cls, *args, **kwargs): print("into A __new__") print(cls) return object.__new__(cls)</code></pre><p>class B(A):<br> def <strong>init</strong>(self, value):<br> print(“into B <strong>init</strong>“)<br> self.value = value</p><pre><code>def __new__(cls, *args, **kwargs): print("into B __new__") print(cls) return super().__new__(A, *args, **kwargs) # 改动了cls变为A</code></pre><p>b = B(10)</p><h1 id="结果：-1"><a href="#结果：-1" class="headerlink" title="结果："></a>结果：</h1><h1 id="into-B-new-1"><a href="#into-B-new-1" class="headerlink" title="into B new"></a>into B <strong>new</strong></h1><h1 id="lt-class-‘main-B’-gt-2"><a href="#lt-class-‘main-B’-gt-2" class="headerlink" title="<class ‘main.B’>"></a><class ‘<strong>main</strong>.B’></h1><h1 id="into-A-new-1"><a href="#into-A-new-1" class="headerlink" title="into A new"></a>into A <strong>new</strong></h1><h1 id="lt-class-‘main-A’-gt"><a href="#lt-class-‘main-A’-gt" class="headerlink" title="<class ‘main.A’>"></a><class ‘<strong>main</strong>.A’></h1><p>into B <strong>new</strong><br><class ‘<strong>main</strong>.B’><br>into A <strong>new</strong><br><class ‘<strong>main</strong>.B’><br>into B <strong>init</strong><br>into B <strong>new</strong><br><class ‘<strong>main</strong>.B’><br>into A <strong>new</strong><br><class ‘<strong>main</strong>.A’></p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">- 若`__new__`没有正确返回当前类`cls`的实例，那`__init__`是不会被调用的，即使是父类的实例也不行，将没有`__init__`被调用。</span><br><span class="line"></span><br><span class="line">【例子】利用`__new__`实现单例模式。</span><br><span class="line"></span><br><span class="line">[70]:</span><br></pre></td></tr></table></figure><p>class Earth:<br> pass</p><p>a = Earth()<br>print(id(a)) # 260728291456<br>b = Earth()<br>print(id(b)) # 260728291624</p><p>class Earth:<br> __instance = None # 定义一个类属性做判断</p><pre><code>def __new__(cls): if cls.__instance is None: cls.__instance = object.__new__(cls) return cls.__instance else: return cls.__instance</code></pre><p>a = Earth()<br>print(id(a)) # 512320401648<br>b = Earth()<br>print(id(b)) # 512320401648<br>2336598724336<br>2336598528464<br>2336598467752<br>2336598467752</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">- `__new__`方法主要是当你继承一些不可变的 class 时（比如`int, str, tuple`）， 提供给你一个自定义这些类的实例化过程的途径。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[71]:</span><br></pre></td></tr></table></figure><p>class CapStr(str):<br> def <strong>new</strong>(cls, string):<br> string = string.upper()<br> return str.<strong>new</strong>(cls, string)</p><p>a = CapStr(“i love lsgogroup”)<br>print(a) # I LOVE LSGOGROUP<br>I LOVE LSGOGROUP</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">- `__del__(self)` 析构器，当一个对象将要被系统回收之时调用的方法。</span><br><span class="line"></span><br><span class="line">> Python 采用自动引用计数（ARC）方式来回收对象所占用的空间，当程序中有一个变量引用该 Python 对象时，Python 会自动保证该对象引用计数为 1；当程序中有两个变量引用该 Python 对象时，Python 会自动保证该对象引用计数为 2，依此类推，如果一个对象的引用计数变成了 0，则说明程序中不再有变量引用该对象，表明程序不再需要该对象，因此 Python 就会回收该对象。</span><br><span class="line">></span><br><span class="line">> 大部分时候，Python 的 ARC 都能准确、高效地回收系统中的每个对象。但如果系统中出现循环引用的情况，比如对象 a 持有一个实例变量引用对象 b，而对象 b 又持有一个实例变量引用对象 a，此时两个对象的引用计数都是 1，而实际上程序已经不再有变量引用它们，系统应该回收它们，此时 Python 的垃圾回收器就可能没那么快，要等专门的循环垃圾回收器（Cyclic Garbage Collector）来检测并回收这种引用循环。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[72]:</span><br></pre></td></tr></table></figure><p>class C(object):<br> def <strong>init</strong>(self):<br> print(‘into C <strong>init</strong>‘)</p><pre><code>def __del__(self): print('into C __del__')</code></pre><p>c1 = C()</p><h1 id="into-C-init"><a href="#into-C-init" class="headerlink" title="into C init"></a>into C <strong>init</strong></h1><p>c2 = c1<br>c3 = c2<br>del c3<br>del c2<br>del c1</p><h1 id="into-C-del"><a href="#into-C-del" class="headerlink" title="into C del"></a>into C <strong>del</strong></h1><p>into C <strong>init</strong><br>into C <strong>del</strong></p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">- `__str__(self)`:</span><br><span class="line"> - 当你打印一个对象的时候，触发`__str__`</span><br><span class="line"> - 当你使用`%s`格式化的时候，触发`__str__`</span><br><span class="line"> - `str`强转数据类型的时候，触发`__str__`</span><br><span class="line">- `__repr__(self)`：</span><br><span class="line"> - `repr`是`str`的备胎</span><br><span class="line"> - 有`__str__`的时候执行`__str__`,没有实现`__str__`的时候，执行`__repr__`</span><br><span class="line"> - `repr(obj)`内置函数对应的结果是`__repr__`的返回值</span><br><span class="line"> - 当你使用`%r`格式化的时候 触发`__repr__`</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[73]:</span><br></pre></td></tr></table></figure><p>class Cat:<br> “””定义一个猫类”””</p><pre><code>def __init__(self, new_name, new_age): """在创建完对象之后 会自动调用, 它完成对象的初始化的功能""" self.name = new_name self.age = new_agedef __str__(self): """返回一个对象的描述信息""" return "名字是:%s , 年龄是:%d" % (self.name, self.age)def __repr__(self): """返回一个对象的描述信息""" return "Cat:(%s,%d)" % (self.name, self.age)def eat(self): print("%s在吃鱼...." % self.name)def drink(self): print("%s在喝可乐..." % self.name)def introduce(self): print("名字是:%s, 年龄是:%d" % (self.name, self.age))</code></pre><h1 id="创建了一个对象"><a href="#创建了一个对象" class="headerlink" title="创建了一个对象"></a>创建了一个对象</h1><p>tom = Cat(“汤姆”, 30)<br>print(tom) # 名字是:汤姆 , 年龄是:30<br>print(str(tom)) # 名字是:汤姆 , 年龄是:30<br>print(repr(tom)) # Cat:(汤姆,30)<br>tom.eat() # 汤姆在吃鱼….<br>tom.introduce() # 名字是:汤姆, 年龄是:30<br>名字是:汤姆 , 年龄是:30<br>名字是:汤姆 , 年龄是:30<br>Cat:(汤姆,30)<br>汤姆在吃鱼….<br>名字是:汤姆, 年龄是:30</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">`__str__(self)` 的返回结果可读性强。也就是说，`__str__` 的意义是得到便于人们阅读的信息，就像下面的 '2019-10-11' 一样。</span><br><span class="line"></span><br><span class="line">`__repr__(self)` 的返回结果应更准确。怎么说，`__repr__` 存在的目的在于调试，便于开发者使用。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[74]:</span><br></pre></td></tr></table></figure><p>import datetime</p><p>today = datetime.date.today()<br>print(str(today)) # 2019-10-11<br>print(repr(today)) # datetime.date(2019, 10, 11)<br>print(‘%s’ %today) # 2019-10-11<br>print(‘%r’ %today) # datetime.date(2019, 10, 11)<br>2020-08-01<br>datetime.date(2020, 8, 1)<br>2020-08-01<br>datetime.date(2020, 8, 1)</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">## 算术运算符</span><br><span class="line"></span><br><span class="line">类型工厂函数，指的是“不通过类而是通过函数来创建对象”。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[75]:</span><br></pre></td></tr></table></figure><p>class C:<br> pass</p><p>print(type(len)) # <class ‘builtin_function_or_method’><br>print(type(dir)) # <class ‘builtin_function_or_method’><br>print(type(int)) # <class ‘type’><br>print(type(list)) # <class ‘type’><br>print(type(tuple)) # <class ‘type’><br>print(type(C)) # <class ‘type’><br>print(int(‘123’)) # 123</p><h1 id="这个例子中list工厂函数把一个元祖对象加工成了一个列表对象。"><a href="#这个例子中list工厂函数把一个元祖对象加工成了一个列表对象。" class="headerlink" title="这个例子中list工厂函数把一个元祖对象加工成了一个列表对象。"></a>这个例子中list工厂函数把一个元祖对象加工成了一个列表对象。</h1><p>print(list((1, 2, 3))) # [1, 2, 3]<br><class ‘builtin_function_or_method’><br><class ‘builtin_function_or_method’><br><class ‘type’><br><class ‘type’><br><class ‘type’><br><class ‘type’><br>123<br>[1, 2, 3]</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">- `__add__(self, other)`定义加法的行为：`+`</span><br><span class="line">- `__sub__(self, other)`定义减法的行为：`-`</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[76]:</span><br></pre></td></tr></table></figure><p>class MyClass:</p><pre><code>def __init__(self, height, weight): self.height = height self.weight = weight# 两个对象的长相加，宽不变.返回一个新的类def __add__(self, others): return MyClass(self.height + others.height, self.weight + others.weight)# 两个对象的宽相减，长不变.返回一个新的类def __sub__(self, others): return MyClass(self.height - others.height, self.weight - others.weight)# 说一下自己的参数def intro(self): print("高为", self.height, " 重为", self.weight)</code></pre><p>def main():<br> a = MyClass(height=10, weight=5)<br> a.intro()</p><pre><code>b = MyClass(height=20, weight=10)b.intro()c = b - ac.intro()d = a + bd.intro()</code></pre><p>if <strong>name</strong> == ‘<strong>main</strong>‘:<br> main()</p><h1 id="高为-10-重为-5"><a href="#高为-10-重为-5" class="headerlink" title="高为 10 重为 5"></a>高为 10 重为 5</h1><h1 id="高为-20-重为-10"><a href="#高为-20-重为-10" class="headerlink" title="高为 20 重为 10"></a>高为 20 重为 10</h1><h1 id="高为-10-重为-5-1"><a href="#高为-10-重为-5-1" class="headerlink" title="高为 10 重为 5"></a>高为 10 重为 5</h1><h1 id="高为-30-重为-15"><a href="#高为-30-重为-15" class="headerlink" title="高为 30 重为 15"></a>高为 30 重为 15</h1><p>高为 10 重为 5<br>高为 20 重为 10<br>高为 10 重为 5<br>高为 30 重为 15</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">- `__mul__(self, other)`定义乘法的行为：`*`</span><br><span class="line">- `__truediv__(self, other)`定义真除法的行为：`/`</span><br><span class="line">- `__floordiv__(self, other)`定义整数除法的行为：`//`</span><br><span class="line">- `__mod__(self, other)` 定义取模算法的行为：`%`</span><br><span class="line">- `__divmod__(self, other)`定义当被 `divmod()` 调用时的行为</span><br><span class="line">- `divmod(a, b)`把除数和余数运算结果结合起来，返回一个包含商和余数的元组`(a // b, a % b)`。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[77]:</span><br></pre></td></tr></table></figure><p>print(divmod(7, 2)) # (3, 1)<br>print(divmod(8, 2)) # (4, 0)<br>(3, 1)<br>(4, 0)</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">- `__pow__(self, other[, module])`定义当被 `power()` 调用或 `**` 运算时的行为</span><br><span class="line">- `__lshift__(self, other)`定义按位左移位的行为：`<<`</span><br><span class="line">- `__rshift__(self, other)`定义按位右移位的行为：`>>`</span><br><span class="line">- `__and__(self, other)`定义按位与操作的行为：`&`</span><br><span class="line">- `__xor__(self, other)`定义按位异或操作的行为：`^`</span><br><span class="line">- `__or__(self, other)`定义按位或操作的行为：`|`</span><br><span class="line"></span><br><span class="line">## 反算术运算符</span><br><span class="line"></span><br><span class="line">反运算魔方方法，与算术运算符保持一一对应，不同之处就是反运算的魔法方法多了一个“r”。当文件左操作不支持相应的操作时被调用。</span><br><span class="line"></span><br><span class="line">- `__radd__(self, other)`定义加法的行为：`+`</span><br><span class="line">- `__rsub__(self, other)`定义减法的行为：`-`</span><br><span class="line">- `__rmul__(self, other)`定义乘法的行为：`*`</span><br><span class="line">- `__rtruediv__(self, other)`定义真除法的行为：`/`</span><br><span class="line">- `__rfloordiv__(self, other)`定义整数除法的行为：`//`</span><br><span class="line">- `__rmod__(self, other)` 定义取模算法的行为：`%`</span><br><span class="line">- `__rdivmod__(self, other)`定义当被 divmod() 调用时的行为</span><br><span class="line">- `__rpow__(self, other[, module])`定义当被 power() 调用或 `**` 运算时的行为</span><br><span class="line">- `__rlshift__(self, other)`定义按位左移位的行为：`<<`</span><br><span class="line">- `__rrshift__(self, other)`定义按位右移位的行为：`>>`</span><br><span class="line">- `__rand__(self, other)`定义按位与操作的行为：`&`</span><br><span class="line">- `__rxor__(self, other)`定义按位异或操作的行为：`^`</span><br><span class="line">- `__ror__(self, other)`定义按位或操作的行为：`|`</span><br></pre></td></tr></table></figure><p>a + b</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">这里加数是`a`，被加数是`b`，因此是`a`主动，反运算就是如果`a`对象的`__add__()`方法没有实现或者不支持相应的操作，那么 Python 就会调用`b`的`__radd__()`方法。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[78]:</span><br></pre></td></tr></table></figure><p>class Nint(int):<br> def <strong>radd</strong>(self, other):<br> return int.<strong>sub</strong>(other, self) # 注意 self 在后面</p><p>a = Nint(5)<br>b = Nint(3)<br>print(a + b) # 8<br>print(1 + b) # -2<br>8<br>-2</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">## 增量赋值运算符</span><br><span class="line"></span><br><span class="line">- `__iadd__(self, other)`定义赋值加法的行为：`+=`</span><br><span class="line">- `__isub__(self, other)`定义赋值减法的行为：`-=`</span><br><span class="line">- `__imul__(self, other)`定义赋值乘法的行为：`*=`</span><br><span class="line">- `__itruediv__(self, other)`定义赋值真除法的行为：`/=`</span><br><span class="line">- `__ifloordiv__(self, other)`定义赋值整数除法的行为：`//=`</span><br><span class="line">- `__imod__(self, other)`定义赋值取模算法的行为：`%=`</span><br><span class="line">- `__ipow__(self, other[, modulo])`定义赋值幂运算的行为：`**=`</span><br><span class="line">- `__ilshift__(self, other)`定义赋值按位左移位的行为：`<<=`</span><br><span class="line">- `__irshift__(self, other)`定义赋值按位右移位的行为：`>>=`</span><br><span class="line">- `__iand__(self, other)`定义赋值按位与操作的行为：`&=`</span><br><span class="line">- `__ixor__(self, other)`定义赋值按位异或操作的行为：`^=`</span><br><span class="line">- `__ior__(self, other)`定义赋值按位或操作的行为：`|=`</span><br><span class="line"></span><br><span class="line">## 一元运算符</span><br><span class="line"></span><br><span class="line">- `__neg__(self)`定义正号的行为：`+x`</span><br><span class="line">- `__pos__(self)`定义负号的行为：`-x`</span><br><span class="line">- `__abs__(self)`定义当被`abs()`调用时的行为</span><br><span class="line">- `__invert__(self)`定义按位求反的行为：`~x`</span><br><span class="line"></span><br><span class="line">## 属性访问</span><br><span class="line"></span><br><span class="line">- `__getattr__(self, name)`: 定义当用户试图获取一个不存在的属性时的行为。</span><br><span class="line">- `__getattribute__(self, name)`：定义当该类的属性被访问时的行为（先调用该方法，查看是否存在该属性，若不存在，接着去调用`__getattr__`）。</span><br><span class="line">- `__setattr__(self, name, value)`：定义当一个属性被设置时的行为。</span><br><span class="line">- `__delattr__(self, name)`：定义当一个属性被删除时的行为。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[79]:</span><br></pre></td></tr></table></figure><p>class C:<br> def <strong>getattribute</strong>(self, item):<br> print(‘<strong>getattribute</strong>‘)<br> return super().<strong>getattribute</strong>(item)</p><pre><code>def __getattr__(self, item): print('__getattr__')def __setattr__(self, key, value): print('__setattr__') super().__setattr__(key, value)def __delattr__(self, item): print('__delattr__') super().__delattr__(item)</code></pre><p>c = C()<br>c.x</p><h1 id="getattribute"><a href="#getattribute" class="headerlink" title="getattribute"></a><strong>getattribute</strong></h1><h1 id="getattr"><a href="#getattr" class="headerlink" title="getattr"></a><strong>getattr</strong></h1><p>c.x = 1</p><h1 id="setattr"><a href="#setattr" class="headerlink" title="setattr"></a><strong>setattr</strong></h1><p>del c.x</p><h1 id="delattr"><a href="#delattr" class="headerlink" title="delattr"></a><strong>delattr</strong></h1><p><strong>getattribute</strong><br><strong>getattr</strong><br><strong>setattr</strong><br><strong>delattr</strong></p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">## 描述符</span><br><span class="line"></span><br><span class="line">描述符就是将某种特殊类型的类的实例指派给另一个类的属性。</span><br><span class="line"></span><br><span class="line">- `__get__(self, instance, owner)`用于访问属性，它返回属性的值。</span><br><span class="line">- `__set__(self, instance, value)`将在属性分配操作中调用，不返回任何内容。</span><br><span class="line">- `__del__(self, instance)`控制删除操作，不返回任何内容。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[80]:</span><br></pre></td></tr></table></figure><p>class MyDecriptor:<br> def <strong>get</strong>(self, instance, owner):<br> print(‘<strong>get</strong>‘, self, instance, owner)</p><pre><code>def __set__(self, instance, value): print('__set__', self, instance, value)def __delete__(self, instance): print('__delete__', self, instance)</code></pre><p>class Test:<br> x = MyDecriptor()</p><p>t = Test()<br>t.x</p><h1 id="get-lt-main-MyDecriptor-object-at-0x000000CEAAEB6B00-gt-lt-main-Test-object-at-0x000000CEABDC0898-gt-lt-class-‘main-Test’-gt"><a href="#get-lt-main-MyDecriptor-object-at-0x000000CEAAEB6B00-gt-lt-main-Test-object-at-0x000000CEABDC0898-gt-lt-class-‘main-Test’-gt" class="headerlink" title="get <main.MyDecriptor object at 0x000000CEAAEB6B00> <main.Test object at 0x000000CEABDC0898> <class ‘main.Test’>"></a><strong>get</strong> <<strong>main</strong>.MyDecriptor object at 0x000000CEAAEB6B00> <<strong>main</strong>.Test object at 0x000000CEABDC0898> <class ‘<strong>main</strong>.Test’></h1><p>t.x = ‘x-man’</p><h1 id="set-lt-main-MyDecriptor-object-at-0x00000023687C6B00-gt-lt-main-Test-object-at-0x00000023696B0940-gt-x-man"><a href="#set-lt-main-MyDecriptor-object-at-0x00000023687C6B00-gt-lt-main-Test-object-at-0x00000023696B0940-gt-x-man" class="headerlink" title="set <main.MyDecriptor object at 0x00000023687C6B00> <main.Test object at 0x00000023696B0940> x-man"></a><strong>set</strong> <<strong>main</strong>.MyDecriptor object at 0x00000023687C6B00> <<strong>main</strong>.Test object at 0x00000023696B0940> x-man</h1><p>del t.x</p><h1 id="delete-lt-main-MyDecriptor-object-at-0x000000EC9B160A90-gt-lt-main-Test-object-at-0x000000EC9B160B38-gt"><a href="#delete-lt-main-MyDecriptor-object-at-0x000000EC9B160A90-gt-lt-main-Test-object-at-0x000000EC9B160B38-gt" class="headerlink" title="delete <main.MyDecriptor object at 0x000000EC9B160A90> <main.Test object at 0x000000EC9B160B38>"></a><strong>delete</strong> <<strong>main</strong>.MyDecriptor object at 0x000000EC9B160A90> <<strong>main</strong>.Test object at 0x000000EC9B160B38></h1><p><strong>get</strong> <<strong>main</strong>.MyDecriptor object at 0x0000022008242668> <<strong>main</strong>.Test object at 0x00000220082427B8> <class ‘<strong>main</strong>.Test’><br><strong>set</strong> <<strong>main</strong>.MyDecriptor object at 0x0000022008242668> <<strong>main</strong>.Test object at 0x00000220082427B8> x-man<br><strong>delete</strong> <<strong>main</strong>.MyDecriptor object at 0x0000022008242668> <<strong>main</strong>.Test object at 0x00000220082427B8></p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">## 定制序列</span><br><span class="line"></span><br><span class="line">协议（Protocols）与其它编程语言中的接口很相似，它规定你哪些方法必须要定义。然而，在 Python 中的协议就显得不那么正式。事实上，在 Python 中，协议更像是一种指南。</span><br><span class="line"></span><br><span class="line">**容器类型的协议**</span><br><span class="line"></span><br><span class="line">- 如果说你希望定制的容器是不可变的话，你只需要定义`__len__()`和`__getitem__()`方法。</span><br><span class="line">- 如果你希望定制的容器是可变的话，除了`__len__()`和`__getitem__()`方法，你还需要定义`__setitem__()`和`__delitem__()`两个方法。</span><br><span class="line"></span><br><span class="line">【例子】编写一个不可改变的自定义列表，要求记录列表中每个元素被访问的次数。</span><br><span class="line"></span><br><span class="line">[81]:</span><br></pre></td></tr></table></figure><p>class CountList:<br> def <strong>init</strong>(self, *args):<br> self.values = [x for x in args]<br> self.count = {}.fromkeys(range(len(self.values)), 0)</p><pre><code>def __len__(self): return len(self.values)def __getitem__(self, item): self.count[item] += 1 return self.values[item]</code></pre><p>c1 = CountList(1, 3, 5, 7, 9)<br>c2 = CountList(2, 4, 6, 8, 10)<br>print(c1[1]) # 3<br>print(c2[2]) # 6<br>print(c1[1] + c2[1]) # 7</p><p>print(c1.count)</p><h1 id="0-0-1-2-2-0-3-0-4-0"><a href="#0-0-1-2-2-0-3-0-4-0" class="headerlink" title="{0: 0, 1: 2, 2: 0, 3: 0, 4: 0}"></a>{0: 0, 1: 2, 2: 0, 3: 0, 4: 0}</h1><p>print(c2.count)</p><h1 id="0-0-1-1-2-1-3-0-4-0"><a href="#0-0-1-1-2-1-3-0-4-0" class="headerlink" title="{0: 0, 1: 1, 2: 1, 3: 0, 4: 0}"></a>{0: 0, 1: 1, 2: 1, 3: 0, 4: 0}</h1><p>3<br>6<br>7<br>{0: 0, 1: 2, 2: 0, 3: 0, 4: 0}<br>{0: 0, 1: 1, 2: 1, 3: 0, 4: 0}</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">- `__len__(self)`定义当被`len()`调用时的行为（返回容器中元素的个数）。</span><br><span class="line">- `__getitem__(self, key)`定义获取容器中元素的行为，相当于`self[key]`。</span><br><span class="line">- `__setitem__(self, key, value)`定义设置容器中指定元素的行为，相当于`self[key] = value`。</span><br><span class="line">- `__delitem__(self, key)`定义删除容器中指定元素的行为，相当于`del self[key]`。</span><br><span class="line"></span><br><span class="line">【例子】编写一个可改变的自定义列表，要求记录列表中每个元素被访问的次数。</span><br><span class="line"></span><br><span class="line">[82]:</span><br></pre></td></tr></table></figure><p>class CountList:<br> def <strong>init</strong>(self, *args):<br> self.values = [x for x in args]<br> self.count = {}.fromkeys(range(len(self.values)), 0)</p><pre><code>def __len__(self): return len(self.values)def __getitem__(self, item): self.count[item] += 1 return self.values[item]def __setitem__(self, key, value): self.values[key] = valuedef __delitem__(self, key): del self.values[key] for i in range(0, len(self.values)): if i >= key: self.count[i] = self.count[i + 1] self.count.pop(len(self.values))</code></pre><p>c1 = CountList(1, 3, 5, 7, 9)<br>c2 = CountList(2, 4, 6, 8, 10)<br>print(c1[1]) # 3<br>print(c2[2]) # 6<br>c2[2] = 12<br>print(c1[1] + c2[2]) # 15<br>print(c1.count)</p><h1 id="0-0-1-2-2-0-3-0-4-0-1"><a href="#0-0-1-2-2-0-3-0-4-0-1" class="headerlink" title="{0: 0, 1: 2, 2: 0, 3: 0, 4: 0}"></a>{0: 0, 1: 2, 2: 0, 3: 0, 4: 0}</h1><p>print(c2.count)</p><h1 id="0-0-1-0-2-2-3-0-4-0"><a href="#0-0-1-0-2-2-3-0-4-0" class="headerlink" title="{0: 0, 1: 0, 2: 2, 3: 0, 4: 0}"></a>{0: 0, 1: 0, 2: 2, 3: 0, 4: 0}</h1><p>del c1[1]<br>print(c1.count)</p><h1 id="0-0-1-0-2-0-3-0"><a href="#0-0-1-0-2-0-3-0" class="headerlink" title="{0: 0, 1: 0, 2: 0, 3: 0}"></a>{0: 0, 1: 0, 2: 0, 3: 0}</h1><p>3<br>6<br>15<br>{0: 0, 1: 2, 2: 0, 3: 0, 4: 0}<br>{0: 0, 1: 0, 2: 2, 3: 0, 4: 0}<br>{0: 0, 1: 0, 2: 0, 3: 0}</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">## 迭代器</span><br><span class="line"></span><br><span class="line">- 迭代是 Python 最强大的功能之一，是访问集合元素的一种方式。</span><br><span class="line">- 迭代器是一个可以记住遍历的位置的对象。</span><br><span class="line">- 迭代器对象从集合的第一个元素开始访问，直到所有的元素被访问完结束。</span><br><span class="line">- 迭代器只能往前不会后退。</span><br><span class="line">- 字符串，列表或元组对象都可用于创建迭代器：</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[84]:</span><br></pre></td></tr></table></figure><p>string = ‘lsgogroup’<br>for c in string:<br> print(c)</p><p>‘’’<br>l<br>s<br>g<br>o<br>g<br>r<br>o<br>u<br>p<br>‘’’</p><p>for c in iter(string):<br> print(c)<br>l<br>s<br>g<br>o<br>g<br>r<br>o<br>u<br>p<br>l<br>s<br>g<br>o<br>g<br>r<br>o<br>u<br>p</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[85]:</span><br></pre></td></tr></table></figure><p>links = {‘B’: ‘百度’, ‘A’: ‘阿里’, ‘T’: ‘腾讯’}<br>for each in links:<br> print(‘%s -> %s’ % (each, links[each]))</p><p>‘’’<br>B -> 百度<br>A -> 阿里<br>T -> 腾讯<br>‘’’</p><p>for each in iter(links):<br> print(‘%s -> %s’ % (each, links[each]))<br>B -> 百度<br>A -> 阿里<br>T -> 腾讯<br>B -> 百度<br>A -> 阿里<br>T -> 腾讯</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">- 迭代器有两个基本的方法：`iter()` 和 `next()`。</span><br><span class="line">- `iter(object)` 函数用来生成迭代器。</span><br><span class="line">- `next(iterator[, default])` 返回迭代器的下一个项目。</span><br><span class="line">- `iterator` -- 可迭代对象</span><br><span class="line">- `default` -- 可选，用于设置在没有下一个元素时返回该默认值，如果不设置，又没有下一个元素则会触发 `StopIteration` 异常。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[2]:</span><br></pre></td></tr></table></figure><p>links = {‘B’: ‘百度’, ‘A’: ‘阿里’, ‘T’: ‘腾讯’}</p><p>it = iter(links)<br>while True:<br> try:<br> each = next(it)<br> except StopIteration:<br> break<br> print(each)</p><h1 id="B"><a href="#B" class="headerlink" title="B"></a>B</h1><h1 id="A"><a href="#A" class="headerlink" title="A"></a>A</h1><h1 id="T"><a href="#T" class="headerlink" title="T"></a>T</h1><p>it = iter(links)<br>print(next(it)) # B<br>print(next(it)) # A<br>print(next(it)) # T<br>print(next(it)) # StopIteration<br>B<br>A<br>T<br>B<br>A<br>T</p><hr><p>StopIteration Traceback (most recent call last)<br><ipython-input-2-682f811edce7> in <module>()<br> 17 print(next(it)) # A<br> 18 print(next(it)) # T<br>—> 19 print(next(it)) # StopIteration</module></ipython-input-2-682f811edce7></p><p>StopIteration: </p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">把一个类作为一个迭代器使用需要在类中实现两个魔法方法 `__iter__()` 与 `__next__()` 。</span><br><span class="line"></span><br><span class="line">- `__iter__(self)`定义当迭代容器中的元素的行为，返回一个特殊的迭代器对象， 这个迭代器对象实现了 `__next__()` 方法并通过 `StopIteration` 异常标识迭代的完成。</span><br><span class="line">- `__next__()` 返回下一个迭代器对象。</span><br><span class="line">- `StopIteration` 异常用于标识迭代的完成，防止出现无限循环的情况，在 `__next__()` 方法中我们可以设置在完成指定循环次数后触发 `StopIteration` 异常来结束迭代。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[88]:</span><br></pre></td></tr></table></figure><p>class Fibs:<br> def <strong>init</strong>(self, n=10):<br> self.a = 0<br> self.b = 1<br> self.n = n</p><pre><code>def __iter__(self): return selfdef __next__(self): self.a, self.b = self.b, self.a + self.b if self.a > self.n: raise StopIteration return self.a</code></pre><p>fibs = Fibs(100)<br>for each in fibs:<br> print(each, end=’ ‘)</p><h1 id="1-1-2-3-5-8-13-21-34-55-89"><a href="#1-1-2-3-5-8-13-21-34-55-89" class="headerlink" title="1 1 2 3 5 8 13 21 34 55 89"></a>1 1 2 3 5 8 13 21 34 55 89</h1><p>1 1 2 3 5 8 13 21 34 55 89 </p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">**4.10 生成器**</span><br><span class="line"></span><br><span class="line">- 在 Python 中，使用了 `yield` 的函数被称为生成器（generator）。</span><br><span class="line">- 跟普通函数不同的是，生成器是一个返回迭代器的函数，只能用于迭代操作，更简单点理解生成器就是一个迭代器。</span><br><span class="line">- 在调用生成器运行的过程中，每次遇到 `yield` 时函数会暂停并保存当前所有的运行信息，返回 `yield` 的值, 并在下一次执行 `next()` 方法时从当前位置继续运行。</span><br><span class="line">- 调用一个生成器函数，返回的是一个迭代器对象。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[6]:</span><br></pre></td></tr></table></figure><p>def myGen():<br> print(‘生成器执行！’)<br> yield 1<br> yield 2</p><p>myG = myGen()<br>for each in myG:<br> print(each)</p><p>‘’’<br>生成器执行！<br>1<br>2<br>‘’’</p><p>myG = myGen()<br>print(next(myG)) </p><h1 id="生成器执行！"><a href="#生成器执行！" class="headerlink" title="生成器执行！"></a>生成器执行！</h1><h1 id="1"><a href="#1" class="headerlink" title="1"></a>1</h1><p>print(next(myG)) # 2<br>print(next(myG)) # StopIteration<br>生成器执行！<br>1<br>2<br>生成器执行！<br>1<br>2</p><hr><p>StopIteration Traceback (most recent call last)<br><ipython-input-6-56bfa60ce8de> in <module>()<br> 14<br> 15 print(next(myG)) # 2<br>—> 16 print(next(myG)) # StopIteration</module></ipython-input-6-56bfa60ce8de></p><p>StopIteration: </p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">【例子】用生成器实现斐波那契数列。</span><br><span class="line"></span><br><span class="line">[93]:</span><br></pre></td></tr></table></figure><p>def libs(n):<br> a = 0<br> b = 1<br> while True:<br> a, b = b, a + b<br> if a > n:<br> return<br> yield a</p><p>for each in libs(100):<br> print(each, end=’ ‘)</p><h1 id="1-1-2-3-5-8-13-21-34-55-89-1"><a href="#1-1-2-3-5-8-13-21-34-55-89-1" class="headerlink" title="1 1 2 3 5 8 13 21 34 55 89"></a>1 1 2 3 5 8 13 21 34 55 89</h1><p>1 1 2 3 5 8 13 21 34 55 89<br>```</p>]]></content>
<summary type="html"><h1 id="Python入门-下"><a href="#Python入门-下" class="headerlink" title="Python入门(下)"></a>Python入门(下)</h1><ol>
<li><a href="https://dsw2-dsw-d202</summary>
<category term="python基础" scheme="https://wicherqaq.github.io/categories/python%E5%9F%BA%E7%A1%80/"/>
</entry>
<entry>
<title>conda源和pip源的转换</title>
<link href="https://wicherqaq.github.io/2020/09/15/conda%E6%BA%90%E5%92%8Cpip%E6%BA%90%E7%9A%84%E8%BD%AC%E6%8D%A2/"/>
<id>https://wicherqaq.github.io/2020/09/15/conda%E6%BA%90%E5%92%8Cpip%E6%BA%90%E7%9A%84%E8%BD%AC%E6%8D%A2/</id>
<published>2020-09-15T00:58:19.000Z</published>
<updated>2020-09-15T00:59:12.582Z</updated>
<content type="html"><![CDATA[<h4 id="conda配置源"><a href="#conda配置源" class="headerlink" title="conda配置源"></a>conda配置源</h4><p>添加清华源</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">conda config --add channels https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/free/</span><br><span class="line">conda config --add channels https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/main/</span><br><span class="line">conda config --add channels https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/conda-forge/</span><br><span class="line">conda config --add channels https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/msys2/</span><br><span class="line">conda config --add channels https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/bioconda/</span><br><span class="line">conda config --add channels https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/menpo/</span><br><span class="line">conda config --add channels https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/pytorch/</span><br><span class="line">conda config --set show_channel_urls yes</span><br></pre></td></tr></table></figure><h4 id="pip配置源（Linux-OSX）"><a href="#pip配置源（Linux-OSX）" class="headerlink" title="pip配置源（Linux/OSX）"></a>pip配置源（Linux/OSX）</h4><ol><li><p>在指定路径下创建配置文件</p><p><code>mkdir ~/.pip</code></p><p><code>vim ~/.pip/pip.conf</code></p></li><li><p>写入配置信息</p></li></ol><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">[global]</span><br><span class="line">index-url=http://mirrors.aliyun.com/pypi/simple/ #源地址</span><br><span class="line"></span><br><span class="line">#豆瓣 http://pypi.douban.com/ </span><br><span class="line">#中国科学技术大学http://pypi.mirrors.ustc.edu.cn/simple/ </span><br><span class="line">#清华：https://pypi.tuna.tsinghua.edu.cn/simple</span><br><span class="line">#阿里云：http://mirrors.aliyun.com/pypi/simple/</span><br><span class="line">#华中理工大学：http://pypi.hustunique.com/</span><br><span class="line">#山东理工大学：http://pypi.sdutlinux.org/</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html"><h4 id="conda配置源"><a href="#conda配置源" class="headerlink" title="conda配置源"></a>conda配置源</h4><p>添加清华源</p>
<figure class="highlight plain"><tab</summary>
<category term="机器学习" scheme="https://wicherqaq.github.io/categories/%E6%9C%BA%E5%99%A8%E5%AD%A6%E4%B9%A0/"/>
<category term="环境搭建" scheme="https://wicherqaq.github.io/tags/%E7%8E%AF%E5%A2%83%E6%90%AD%E5%BB%BA/"/>
</entry>
<entry>
<title>ubuntu双网卡网络设置</title>
<link href="https://wicherqaq.github.io/2020/09/10/ubuntu%E5%8F%8C%E7%BD%91%E5%8D%A1%E7%BD%91%E7%BB%9C%E8%AE%BE%E7%BD%AE/"/>
<id>https://wicherqaq.github.io/2020/09/10/ubuntu%E5%8F%8C%E7%BD%91%E5%8D%A1%E7%BD%91%E7%BB%9C%E8%AE%BE%E7%BD%AE/</id>
<published>2020-09-10T03:17:13.000Z</published>
<updated>2020-09-10T03:20:01.514Z</updated>
<content type="html"><![CDATA[<h4 id="当前操作"><a href="#当前操作" class="headerlink" title="当前操作"></a>当前操作</h4><p>在<code>/etc/rc.local</code>启动文件中添加<code>route add</code>命令指定网段，网卡和网关信息</p><p>sudo route add -net 192.168.8.0/24 【内网网卡名】</p><p>sudo route add -net 192.168.8.0/24 gw 192.168.8.1 # 路由网关地址</p><p>sudo route add -net 192.168.10.0/24 【外网网卡名】</p><p>sudo route add -net 192.168.10.0/24 gw 192.168.10.1 # 路由网关地址</p><h5 id="route-n"><a href="#route-n" class="headerlink" title="route -n"></a>route -n</h5><p>查看路由表</p><h5 id="route-add"><a href="#route-add" class="headerlink" title="route add"></a>route add</h5><p><em>命令解释</em>：<code>route add</code>命令的主要作用是添加静态路由</p><h5 id="route-del"><a href="#route-del" class="headerlink" title="route del"></a>route del</h5><p><em>命令解释</em>：<code>route del</code>命令的主要作用是删除<code>route -n</code>列出的静态路由。（网段相同，掩码相同则从上到下一条条删除）</p><p><em>注意</em>：直接在命令行下执行route命令来添加路由，不会永久保存，当网卡重启或者机器重启之后，该路由就失效了；可以在/etc/rc.local中添加route命令来设置路由永久有效。</p><h4 id="目前遇到的问题"><a href="#目前遇到的问题" class="headerlink" title="目前遇到的问题"></a>目前遇到的问题</h4><ol><li><p>ping <a href="http://www.baidu.com" target="_blank" rel="noopener">www.baidu.com</a> 可以ping通</p><p>但是ping局域网内的其他机器会没有反应（怀疑是不是huawei路由器的问题-待验证）</p></li><li><p>指定相关<code>IP</code>到指定的网卡，使得访问只能走指定的网关（目前思路：可能需要修改<code>host</code>文件？通过<code>route add</code>命令设置到指定网关）</p></li></ol>]]></content>
<summary type="html"><h4 id="当前操作"><a href="#当前操作" class="headerlink" title="当前操作"></a>当前操作</h4><p>在<code>/etc/rc.local</code>启动文件中添加<code>route add</code>命令指定网段</summary>
<category term="Linux" scheme="https://wicherqaq.github.io/categories/Linux/"/>
<category term="ubuntu" scheme="https://wicherqaq.github.io/tags/ubuntu/"/>
</entry>
<entry>
<title>位运算</title>
<link href="https://wicherqaq.github.io/2020/09/10/%E4%BD%8D%E8%BF%90%E7%AE%97/"/>
<id>https://wicherqaq.github.io/2020/09/10/%E4%BD%8D%E8%BF%90%E7%AE%97/</id>
<published>2020-09-10T02:51:47.000Z</published>
<updated>2020-09-10T02:54:33.772Z</updated>
<content type="html"><![CDATA[<h1 id="位运算"><a href="#位运算" class="headerlink" title="位运算"></a>位运算</h1><p>[TOC]</p><h2 id="1-原码、反码和补码"><a href="#1-原码、反码和补码" class="headerlink" title="1. 原码、反码和补码"></a>1. 原码、反码和补码</h2><p>二进制有三种不同的表示形式：原码、反码和补码，计算机内部使用补码来表示。</p><p><strong>原码</strong>：就是其二进制表示（注意，有一位符号位）。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">00 00 00 11 -> 3</span><br><span class="line">10 00 00 11 -> -3</span><br></pre></td></tr></table></figure><p><strong>反码</strong>：正数的反码就是原码，负数的反码是符号位不变，其余位取反（对应正数按位取反）。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">00 00 00 11 -> 3</span><br><span class="line">11 11 11 00 -> -3</span><br></pre></td></tr></table></figure><p><strong>补码</strong>：正数的补码就是原码，负数的补码是反码+1。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">00 00 00 11 -> 3</span><br><span class="line">11 11 11 01 -> -3</span><br></pre></td></tr></table></figure><p><strong>符号位</strong>：最高位为符号位，0表示正数，1表示负数。在位运算中符号位也参与运算。</p><h2 id="2-按位运算"><a href="#2-按位运算" class="headerlink" title="2. 按位运算"></a>2. 按位运算</h2><ul><li>按位非操作 ~</li></ul><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">~ <span class="number">1</span> = <span class="number">0</span></span><br><span class="line">~ <span class="number">0</span> = <span class="number">1</span></span><br></pre></td></tr></table></figure><p><code>~</code> 把<code>num</code>的补码中的 0 和 1 全部取反（0 变为 1，1 变为 0）有符号整数的符号位在 <code>~</code> 运算中同样会取反。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">00 00 01 01 -> 5</span><br><span class="line">~</span><br><span class="line">---</span><br><span class="line">11 11 10 10 -> -6</span><br><span class="line"></span><br><span class="line">11 11 10 11 -> -5</span><br><span class="line">~</span><br><span class="line">---</span><br><span class="line">00 00 01 00 -> 4</span><br></pre></td></tr></table></figure><ul><li>按位与操作 &</li></ul><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1</span> & <span class="number">1</span> = <span class="number">1</span></span><br><span class="line"><span class="number">1</span> & <span class="number">0</span> = <span class="number">0</span></span><br><span class="line"><span class="number">0</span> & <span class="number">1</span> = <span class="number">0</span></span><br><span class="line"><span class="number">0</span> & <span class="number">0</span> = <span class="number">0</span></span><br></pre></td></tr></table></figure><p>只有两个对应位都为 1 时才为 1</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">00 00 01 01 -> 5</span><br><span class="line">&</span><br><span class="line">00 00 01 10 -> 6</span><br><span class="line">---</span><br><span class="line">00 00 01 00 -> 4</span><br></pre></td></tr></table></figure><ul><li>按位或操作 |</li></ul><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1</span> | <span class="number">1</span> = <span class="number">1</span></span><br><span class="line"><span class="number">1</span> | <span class="number">0</span> = <span class="number">1</span></span><br><span class="line"><span class="number">0</span> | <span class="number">1</span> = <span class="number">1</span></span><br><span class="line"><span class="number">0</span> | <span class="number">0</span> = <span class="number">0</span></span><br></pre></td></tr></table></figure><p>只要两个对应位中有一个 1 时就为 1</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">00 00 01 01 -> 5</span><br><span class="line">|</span><br><span class="line">00 00 01 10 -> 6</span><br><span class="line">---</span><br><span class="line">00 00 01 11 -> 7</span><br></pre></td></tr></table></figure><ul><li>按位异或操作 ^</li></ul><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1</span> ^ <span class="number">1</span> = <span class="number">0</span></span><br><span class="line"><span class="number">1</span> ^ <span class="number">0</span> = <span class="number">1</span></span><br><span class="line"><span class="number">0</span> ^ <span class="number">1</span> = <span class="number">1</span></span><br><span class="line"><span class="number">0</span> ^ <span class="number">0</span> = <span class="number">0</span></span><br></pre></td></tr></table></figure><p>只有两个对应位不同时才为 1</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">00 00 01 01 -> 5</span><br><span class="line">^</span><br><span class="line">00 00 01 10 -> 6</span><br><span class="line">---</span><br><span class="line">00 00 00 11 -> 3</span><br></pre></td></tr></table></figure><p>异或操作的性质：满足交换律和结合律</p><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">A: <span class="number">00</span> <span class="number">00</span> <span class="number">11</span> <span class="number">00</span></span><br><span class="line">B: <span class="number">00</span> <span class="number">00</span> <span class="number">01</span> <span class="number">11</span></span><br><span class="line"></span><br><span class="line">A^B: <span class="number">00</span> <span class="number">00</span> <span class="number">10</span> <span class="number">11</span></span><br><span class="line">B^A: <span class="number">00</span> <span class="number">00</span> <span class="number">10</span> <span class="number">11</span></span><br><span class="line"></span><br><span class="line">A^A: <span class="number">00</span> <span class="number">00</span> <span class="number">00</span> <span class="number">00</span></span><br><span class="line">A^<span class="number">0</span>: <span class="number">00</span> <span class="number">00</span> <span class="number">11</span> <span class="number">00</span></span><br><span class="line"></span><br><span class="line">A^B^A: = A^A^B = B = <span class="number">00</span> <span class="number">00</span> <span class="number">01</span> <span class="number">11</span></span><br></pre></td></tr></table></figure><ul><li>按位左移操作 <<</li></ul><p><code>num << i</code> 将<code>num</code>的二进制表示向左移动<code>i</code>位所得的值。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">00 00 10 11 -> 11</span><br><span class="line"><span class="number">11</span> << <span class="number">3</span></span><br><span class="line">---</span><br><span class="line">01 01 10 00 -> 88</span><br></pre></td></tr></table></figure><ul><li>按位右移操作 >></li></ul><p><code>num >> i</code> 将<code>num</code>的二进制表示向右移动<code>i</code>位所得的值。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">00 00 10 11 -> 11</span><br><span class="line"><span class="number">11</span> >> <span class="number">2</span></span><br><span class="line">---</span><br><span class="line">00 00 00 10 -> 2</span><br></pre></td></tr></table></figure><h2 id="3-利用位运算实现快速计算"><a href="#3-利用位运算实现快速计算" class="headerlink" title="3. 利用位运算实现快速计算"></a>3. 利用位运算实现快速计算</h2><p>通过 <code><<</code>，<code>>></code> 快速计算2的倍数问题。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">n << 1 -> 计算 n*2</span><br><span class="line">n >> 1 -> 计算 n/2，负奇数的运算不可用</span><br><span class="line">n << m -> 计算 n*(2^m)，即乘以 2 的 m 次方</span><br><span class="line">n >> m -> 计算 n/(2^m)，即除以 2 的 m 次方</span><br><span class="line">1 << n -> 2^n</span><br></pre></td></tr></table></figure><p>通过 <code>^</code> 快速交换两个整数。 通过 <code>^</code> 快速交换两个整数。</p><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">a ^= b</span><br><span class="line">b ^= a</span><br><span class="line">a ^= b</span><br></pre></td></tr></table></figure><p>通过 <code>a & (-a)</code> 快速获取<code>a</code>的最后为 1 位置的整数。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">00 00 01 01 -> 5</span><br><span class="line">&</span><br><span class="line">11 11 10 11 -> -5</span><br><span class="line">---</span><br><span class="line">00 00 00 01 -> 1</span><br><span class="line"></span><br><span class="line">00 00 11 10 -> 14</span><br><span class="line">&</span><br><span class="line">11 11 00 10 -> -14</span><br><span class="line">---</span><br><span class="line">00 00 00 10 -> 2</span><br></pre></td></tr></table></figure><h2 id="4-利用位运算实现整数集合"><a href="#4-利用位运算实现整数集合" class="headerlink" title="4. 利用位运算实现整数集合"></a>4. 利用位运算实现整数集合</h2><p>一个数的二进制表示可以看作是一个集合（0 表示不在集合中，1 表示在集合中）。</p><p>比如集合 <code>{1, 3, 4, 8}</code>，可以表示成 <code>01 00 01 10 10</code> 而对应的位运算也就可以看作是对集合进行的操作。</p><p>元素与集合的操作：</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">a | (1<<i) -> 把 i 插入到集合中</span><br><span class="line">a & ~(1<<i) -> 把 i 从集合中删除</span><br><span class="line">a & (1<<i) -> 判断 i 是否属于该集合（零不属于，非零属于）</span><br></pre></td></tr></table></figure><p>集合之间的操作：</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">a 补 -> ~a</span><br><span class="line">a 交 b -> a & b</span><br><span class="line">a 并 b -> a | b</span><br><span class="line">a 差 b -> a & (~b)</span><br></pre></td></tr></table></figure><p>注意：整数在内存中是以补码的形式存在的，输出自然也是按照补码输出。</p><p>【例子】C#语言输出负数。</p><p>[ ]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">class Program</span><br><span class="line">{</span><br><span class="line"> static void Main(string[] args)</span><br><span class="line"> {</span><br><span class="line"> string s1 = Convert.ToString(-3, 2);</span><br><span class="line"> Console.WriteLine(s1); </span><br><span class="line"> // 11111111111111111111111111111101</span><br><span class="line"> </span><br><span class="line"> string s2 = Convert.ToString(-3, 16);</span><br><span class="line"> Console.WriteLine(s2); </span><br><span class="line"> // fffffffd</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>【例子】 Python 的<code>bin()</code> 输出。</p><p>[37]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">print(bin(3)) # 0b11</span><br><span class="line">print(bin(-3)) # -0b11</span><br><span class="line"></span><br><span class="line">print(bin(-3 & 0xffffffff)) </span><br><span class="line"># 0b11111111111111111111111111111101</span><br><span class="line"></span><br><span class="line">print(bin(0xfffffffd)) </span><br><span class="line"># 0b11111111111111111111111111111101</span><br><span class="line"></span><br><span class="line">print(0xfffffffd) # 4294967293</span><br><span class="line">0b11</span><br><span class="line">-0b11</span><br><span class="line">0b11111111111111111111111111111101</span><br><span class="line">0b11111111111111111111111111111101</span><br><span class="line">4294967293</span><br></pre></td></tr></table></figure><p>是不是很颠覆认知，我们从结果可以看出：</p><ul><li>Python中<code>bin</code>一个负数（十进制表示），输出的是它的原码的二进制表示加上个负号，巨坑。</li><li>Python中的整型是补码形式存储的。</li><li>Python中整型是不限制长度的不会超范围溢出。</li></ul><p>所以为了获得负数（十进制表示）的补码，需要手动将其和十六进制数<code>0xffffffff</code>进行按位与操作，再交给<code>bin()</code>进行输出，得到的才是负数的补码表示。</p>]]></content>
<summary type="html"><h1 id="位运算"><a href="#位运算" class="headerlink" title="位运算"></a>位运算</h1><p>[TOC]</p>
<h2 id="1-原码、反码和补码"><a href="#1-原码、反码和补码" class="headerl</summary>
<category term="计算机基础" scheme="https://wicherqaq.github.io/categories/%E8%AE%A1%E7%AE%97%E6%9C%BA%E5%9F%BA%E7%A1%80/"/>
</entry>
<entry>
<title>python入门（中）</title>
<link href="https://wicherqaq.github.io/2020/09/10/python%E5%85%A5%E9%97%A8%EF%BC%88%E4%B8%AD%EF%BC%89/"/>
<id>https://wicherqaq.github.io/2020/09/10/python%E5%85%A5%E9%97%A8%EF%BC%88%E4%B8%AD%EF%BC%89/</id>
<published>2020-09-10T02:51:26.000Z</published>
<updated>2020-09-10T02:56:57.752Z</updated>
<content type="html"><![CDATA[<h1 id="Python入门-中"><a href="#Python入门-中" class="headerlink" title="Python入门(中)"></a>Python入门(中)</h1><p>[TOC]</p><h1 id="简介"><a href="#简介" class="headerlink" title="简介"></a>简介</h1><p>Python 是一种通用编程语言，其在科学计算和机器学习领域具有广泛的应用。如果我们打算利用 Python 来执行机器学习，那么对 Python 有一些基本的了解就是至关重要的。本 Python 入门系列体验就是为这样的初学者精心准备的。</p><p><strong>本实验包括以下内容</strong>：</p><ol><li>列表<ul><li>列表的定义</li><li>列表的创建</li><li>向列表中添加元素</li><li>删除列表中的元素</li><li>获取列表中的元素</li><li>列表的常用操作符</li><li>列表的其他方法</li></ul></li><li>元组<ul><li>创建和访问一个元组</li><li>更新和删除一个元组</li><li>元组相关的操作符</li><li>内置方法</li><li>解压元组</li></ul></li><li>字符串<ul><li>字符串的定义</li><li>字符串的切片与拼接</li><li>字符串的常用内置方法</li><li>字符串格式化</li></ul></li><li>字典<ul><li>可变类型与不可变类型</li><li>字典的定义</li><li>创建和访问字典</li><li>字典的内置方法</li></ul></li><li>集合<ul><li>集合的创建</li><li>访问集合中的值</li><li>集合的内置方法</li><li>集合的转换</li><li>不可变集合</li></ul></li><li>序列<ul><li>针对序列的内置函数</li></ul></li></ol><h1 id="列表"><a href="#列表" class="headerlink" title="列表"></a>列表</h1><p>简单数据类型</p><ul><li>整型<code><class 'int'></code></li><li>浮点型<code><class 'float'></code></li><li>布尔型<code><class 'bool'></code></li></ul><p>容器数据类型</p><ul><li>列表<code><class 'list'></code></li><li>元组<code><class 'tuple'></code></li><li>字典<code><class 'dict'></code></li><li>集合<code><class 'set'></code></li><li>字符串<code><class 'str'></code></li></ul><h2 id="1-列表的定义"><a href="#1-列表的定义" class="headerlink" title="1. 列表的定义"></a>1. 列表的定义</h2><p>列表是有序集合，没有固定大小，能够保存任意数量任意类型的 Python 对象，语法为 <code>[元素1, 元素2, ..., 元素n]</code>。</p><ul><li>关键点是「中括号 []」和「逗号 ,」</li><li>中括号 把所有元素绑在一起</li><li>逗号 将每个元素一一分开</li></ul><h2 id="2-列表的创建"><a href="#2-列表的创建" class="headerlink" title="2. 列表的创建"></a>2. 列表的创建</h2><ul><li>创建一个普通列表</li></ul><p>【例子】</p><p>[1]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">x = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">print(x, type(x))</span><br><span class="line"># ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday'] <class 'list'></span><br><span class="line"></span><br><span class="line">x = [2, 3, 4, 5, 6, 7]</span><br><span class="line">print(x, type(x))</span><br><span class="line"># [2, 3, 4, 5, 6, 7] <class 'list'></span><br><span class="line">['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday'] <class 'list'></span><br><span class="line">hello</span><br><span class="line">[2, 3, 4, 5, 6, 7] <class 'list'></span><br></pre></td></tr></table></figure><ul><li>利用<code>range()</code>创建列表</li></ul><p>【例子】</p><p>[2]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">x = list(range(10))</span><br><span class="line">print(x, type(x))</span><br><span class="line"># [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] <class 'list'></span><br><span class="line"></span><br><span class="line">x = list(range(1, 11, 2))</span><br><span class="line">print(x, type(x))</span><br><span class="line"># [1, 3, 5, 7, 9] <class 'list'></span><br><span class="line"></span><br><span class="line">x = list(range(10, 1, -2))</span><br><span class="line">print(x, type(x))</span><br><span class="line"># [10, 8, 6, 4, 2] <class 'list'></span><br><span class="line">[0, 1, 2, 3, 4, 5, 6, 7, 8, 9] <class 'list'></span><br><span class="line">[1, 3, 5, 7, 9] <class 'list'></span><br><span class="line">[10, 8, 6, 4, 2] <class 'list'></span><br></pre></td></tr></table></figure><ul><li>利用推导式创建列表</li></ul><p>【例子】</p><p>[3]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br></pre></td><td class="code"><pre><span class="line">x = [0] * 5</span><br><span class="line">print(x, type(x))</span><br><span class="line"># [0, 0, 0, 0, 0] <class 'list'></span><br><span class="line"></span><br><span class="line">x = [0 for i in range(5)]</span><br><span class="line">print(x, type(x))</span><br><span class="line"># [0, 0, 0, 0, 0] <class 'list'></span><br><span class="line"></span><br><span class="line">x = [i for i in range(10)]</span><br><span class="line">print(x, type(x))</span><br><span class="line"># [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] <class 'list'></span><br><span class="line"></span><br><span class="line">x = [i for i in range(1, 10, 2)]</span><br><span class="line">print(x, type(x))</span><br><span class="line"># [1, 3, 5, 7, 9] <class 'list'></span><br><span class="line"></span><br><span class="line">x = [i for i in range(10, 1, -2)]</span><br><span class="line">print(x, type(x))</span><br><span class="line"># [10, 8, 6, 4, 2] <class 'list'></span><br><span class="line"></span><br><span class="line">x = [i ** 2 for i in range(1, 10)]</span><br><span class="line">print(x, type(x))</span><br><span class="line"># [1, 4, 9, 16, 25, 36, 49, 64, 81] <class 'list'></span><br><span class="line"></span><br><span class="line">x = [i for i in range(100) if (i % 2) != 0 and (i % 3) == 0]</span><br><span class="line">print(x, type(x))</span><br><span class="line"></span><br><span class="line"># [3, 9, 15, 21, 27, 33, 39,</span><br><span class="line">[0, 0, 0, 0, 0] <class 'list'></span><br><span class="line">[0, 0, 0, 0, 0] <class 'list'></span><br><span class="line">[0, 1, 2, 3, 4, 5, 6, 7, 8, 9] <class 'list'></span><br><span class="line">[1, 3, 5, 7, 9] <class 'list'></span><br><span class="line">[10, 8, 6, 4, 2] <class 'list'></span><br><span class="line">[1, 4, 9, 16, 25, 36, 49, 64, 81] <class 'list'></span><br><span class="line">[3, 9, 15, 21, 27, 33, 39, 45, 51, 57, 63, 69, 75, 81, 87, 93, 99] <class 'list'></span><br></pre></td></tr></table></figure><p>注意：</p><p>由于list的元素可以是任何对象，因此列表中所保存的是对象的指针。即使保存一个简单的<code>[1,2,3]</code>，也有3个指针和3个整数对象。</p><p><code>x = [a] * 4</code>操作中，只是创建4个指向list的引用，所以一旦<code>a</code>改变，<code>x</code>中4个<code>a</code>也会随之改变。</p><p>【例子】</p><p>[4]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line">x = [[0] * 3] * 4</span><br><span class="line">print(x, type(x))</span><br><span class="line"># [[0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0]] <class 'list'></span><br><span class="line"></span><br><span class="line">x[0][0] = 1</span><br><span class="line">print(x, type(x))</span><br><span class="line"># [[1, 0, 0], [1, 0, 0], [1, 0, 0], [1, 0, 0]] <class 'list'></span><br><span class="line"></span><br><span class="line">a = [0] * 3</span><br><span class="line">x = [a] * 4</span><br><span class="line">print(x, type(x))</span><br><span class="line"># [[0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0]] <class 'list'></span><br><span class="line"></span><br><span class="line">x[0][0] = 1</span><br><span class="line">print(x, type(x))</span><br><span class="line"># [[1, 0, 0], [1, 0, 0], [1, 0, 0], [1, 0, 0]] <class 'list'></span><br><span class="line">[[0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0]] <class 'list'></span><br><span class="line">[[1, 0, 0], [1, 0, 0], [1, 0, 0], [1, 0, 0]] <class 'list'></span><br><span class="line">[[0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0]] <class 'list'></span><br><span class="line">[[1, 0, 0], [1, 0, 0], [1, 0, 0], [1, 0, 0]] <class 'list'></span><br></pre></td></tr></table></figure><ul><li>创建一个混合列表</li></ul><p>【例子】</p><p>[5]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">mix = [1, 'lsgo', 3.14, [1, 2, 3]]</span><br><span class="line">print(mix, type(mix)) </span><br><span class="line"># [1, 'lsgo', 3.14, [1, 2, 3]] <class 'list'></span><br><span class="line">[1, 'lsgo', 3.14, [1, 2, 3]] <class 'list'></span><br></pre></td></tr></table></figure><ul><li>创建一个空列表</li></ul><p>【例子】</p><p>[6]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">empty = []</span><br><span class="line">print(empty, type(empty)) # [] <class 'list'></span><br><span class="line">[] <class 'list'></span><br></pre></td></tr></table></figure><p>列表不像元组，列表内容可更改 (mutable)，因此附加 (<code>append</code>, <code>extend</code>)、插入 (<code>insert</code>)、删除 (<code>remove</code>, <code>pop</code>) 这些操作都可以用在它身上。</p><h2 id="3-向列表中添加元素"><a href="#3-向列表中添加元素" class="headerlink" title="3. 向列表中添加元素"></a>3. 向列表中添加元素</h2><ul><li><code>list.append(obj)</code> 在列表末尾添加新的对象，只接受一个参数，参数可以是任何数据类型，被追加的元素在 list 中保持着原结构类型。</li></ul><p>【例子】</p><p>[7]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">x = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">x.append('Thursday')</span><br><span class="line">print(x) </span><br><span class="line"># ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Thursday']</span><br><span class="line"></span><br><span class="line">print(len(x)) # 6</span><br><span class="line">['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Thursday']</span><br><span class="line">6</span><br></pre></td></tr></table></figure><p>此元素如果是一个 list，那么这个 list 将作为一个整体进行追加，注意<code>append()</code>和<code>extend()</code>的区别。</p><p>【例子】</p><p>[8]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">x = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">x.append(['Thursday', 'Sunday'])</span><br><span class="line">print(x) </span><br><span class="line"># ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', ['Thursday', 'Sunday']]</span><br><span class="line"></span><br><span class="line">print(len(x)) # 6</span><br><span class="line">['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', ['Thursday', 'Sunday']]</span><br><span class="line">6</span><br></pre></td></tr></table></figure><ul><li><code>list.extend(seq)</code> 在列表末尾一次性追加另一个序列中的多个值（用新列表扩展原来的列表）</li></ul><p>【例子】</p><p>[9]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">x = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">x.extend(['Thursday', 'Sunday'])</span><br><span class="line">print(x) </span><br><span class="line"># ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Thursday', 'Sunday']</span><br><span class="line"></span><br><span class="line">print(len(x)) # 7</span><br><span class="line">['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Thursday', 'Sunday']</span><br><span class="line">7</span><br></pre></td></tr></table></figure><p>严格来说 <code>append</code> 是追加，把一个东西整体添加在列表后，而 <code>extend</code> 是扩展，把一个东西里的所有元素添加在列表后。</p><ul><li><code>list.insert(index, obj)</code> 在编号 <code>index</code> 位置插入 <code>obj</code>。</li></ul><p>【例子】</p><p>[10]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">x = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">x.insert(2, 'Sunday')</span><br><span class="line">print(x)</span><br><span class="line"># ['Monday', 'Tuesday', 'Sunday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line"></span><br><span class="line">print(len(x)) # 6</span><br><span class="line">['Monday', 'Tuesday', 'Sunday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">6</span><br></pre></td></tr></table></figure><h2 id="4-删除列表中的元素"><a href="#4-删除列表中的元素" class="headerlink" title="4. 删除列表中的元素"></a>4. 删除列表中的元素</h2><ul><li><code>list.remove(obj)</code> 移除列表中某个值的第一个匹配项</li></ul><p>【例子】</p><p>[11]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">x = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">x.remove('Monday')</span><br><span class="line">print(x) # ['Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">['Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br></pre></td></tr></table></figure><ul><li><code>list.pop([index=-1])</code> 移除列表中的一个元素（默认最后一个元素），并且返回该元素的值</li></ul><p>【例子】</p><p>[12]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">x = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">y = x.pop()</span><br><span class="line">print(y) # Friday</span><br><span class="line"></span><br><span class="line">y = x.pop(0)</span><br><span class="line">print(y) # Monday</span><br><span class="line"></span><br><span class="line">y = x.pop(-2)</span><br><span class="line">print(y) # Wednesday</span><br><span class="line">print(x) # ['Tuesday', 'Thursday']</span><br><span class="line">Friday</span><br><span class="line">Monday</span><br><span class="line">Wednesday</span><br><span class="line">['Tuesday', 'Thursday']</span><br></pre></td></tr></table></figure><p><code>remove</code> 和 <code>pop</code> 都可以删除元素，前者是指定具体要删除的元素，后者是指定一个索引。</p><ul><li><code>del var1[, var2 ……]</code> 删除单个或多个对象。</li></ul><p>【例子】</p><p>如果知道要删除的元素在列表中的位置，可使用<code>del</code>语句。</p><p>[13]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">x = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">del x[0:2]</span><br><span class="line">print(x) # ['Wednesday', 'Thursday', 'Friday']</span><br><span class="line">['Wednesday', 'Thursday', 'Friday']</span><br></pre></td></tr></table></figure><p>如果你要从列表中删除一个元素，且不再以任何方式使用它，就使用<code>del</code>语句；如果你要在删除元素后还能继续使用它，就使用方法<code>pop()</code>。</p><h2 id="5-获取列表中的元素"><a href="#5-获取列表中的元素" class="headerlink" title="5. 获取列表中的元素"></a>5. 获取列表中的元素</h2><ul><li>通过元素的索引值，从列表获取单个元素，注意，列表索引值是从0开始的。</li><li>通过将索引指定为-1，可让Python返回最后一个列表元素，索引 -2 返回倒数第二个列表元素，以此类推。</li></ul><p>【例子】</p><p>[14]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">x = ['Monday', 'Tuesday', 'Wednesday', ['Thursday', 'Friday']]</span><br><span class="line">print(x[0], type(x[0])) # Monday <class 'str'></span><br><span class="line">print(x[-1], type(x[-1])) # ['Thursday', 'Friday'] <class 'list'></span><br><span class="line">print(x[-2], type(x[-2])) # Wednesday <class 'str'></span><br><span class="line">Monday <class 'str'></span><br><span class="line">['Thursday', 'Friday'] <class 'list'></span><br><span class="line">Wednesday <class 'str'></span><br></pre></td></tr></table></figure><p>切片的通用写法是 <code>start : stop : step</code></p><ul><li>情况 1 - “start :”</li><li>以 <code>step</code> 为 1 (默认) 从编号 <code>start</code> 往列表尾部切片。</li></ul><p>【例子】</p><p>[15]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">x = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">print(x[3:]) # ['Thursday', 'Friday']</span><br><span class="line">print(x[-3:]) # ['Wednesday', 'Thursday', 'Friday']</span><br><span class="line">['Thursday', 'Friday']</span><br><span class="line">['Wednesday', 'Thursday', 'Friday']</span><br></pre></td></tr></table></figure><ul><li>情况 2 - “: stop”</li><li>以 <code>step</code> 为 1 (默认) 从列表头部往编号 <code>stop</code> 切片。</li></ul><p>【例子】</p><p>[16]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">print(week[:3]) # ['Monday', 'Tuesday', 'Wednesday']</span><br><span class="line">print(week[:-3]) # ['Monday', 'Tuesday']</span><br><span class="line">['Monday', 'Tuesday', 'Wednesday']</span><br><span class="line">['Monday', 'Tuesday']</span><br></pre></td></tr></table></figure><ul><li>情况 3 - “start : stop”</li><li>以 <code>step</code> 为 1 (默认) 从编号 <code>start</code> 往编号 <code>stop</code> 切片。</li></ul><p>【例子】</p><p>[17]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">print(week[1:3]) # ['Tuesday', 'Wednesday']</span><br><span class="line">print(week[-3:-1]) # ['Wednesday', 'Thursday']</span><br><span class="line">['Tuesday', 'Wednesday']</span><br><span class="line">['Wednesday', 'Thursday']</span><br></pre></td></tr></table></figure><ul><li>情况 4 - “start : stop : step”</li><li>以具体的 <code>step</code> 从编号 <code>start</code> 往编号 <code>stop</code> 切片。注意最后把 <code>step</code> 设为 -1，相当于将列表反向排列。</li></ul><p>【例子】</p><p>[18]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">print(week[1:4:2]) # ['Tuesday', 'Thursday']</span><br><span class="line">print(week[:4:2]) # ['Monday', 'Wednesday']</span><br><span class="line">print(week[1::2]) # ['Tuesday', 'Thursday']</span><br><span class="line">print(week[::-1]) </span><br><span class="line"># ['Friday', 'Thursday', 'Wednesday', 'Tuesday', 'Monday']</span><br><span class="line">['Tuesday', 'Thursday']</span><br><span class="line">['Monday', 'Wednesday']</span><br><span class="line">['Tuesday', 'Thursday']</span><br><span class="line">['Friday', 'Thursday', 'Wednesday', 'Tuesday', 'Monday']</span><br></pre></td></tr></table></figure><ul><li>情况 5 - “ : “</li><li>复制列表中的所有元素（浅拷贝）。</li></ul><p>【例子】</p><p>[19]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">eek = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">print(week[:]) </span><br><span class="line"># ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br><span class="line">['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']</span><br></pre></td></tr></table></figure><p>【例子】浅拷贝与深拷贝</p><p>[20]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line">list1 = [123, 456, 789, 213]</span><br><span class="line">list2 = list1</span><br><span class="line">list3 = list1[:]</span><br><span class="line"></span><br><span class="line">print(list2) # [123, 456, 789, 213]</span><br><span class="line">print(list3) # [123, 456, 789, 213]</span><br><span class="line">list1.sort()</span><br><span class="line">print(list2) # [123, 213, 456, 789] </span><br><span class="line">print(list3) # [123, 456, 789, 213]</span><br><span class="line"></span><br><span class="line">list1 = [[123, 456], [789, 213]]</span><br><span class="line">list2 = list1</span><br><span class="line">list3 = list1[:]</span><br><span class="line">print(list2) # [[123, 456], [789, 213]]</span><br><span class="line">print(list3) # [[123, 456], [789, 213]]</span><br><span class="line">list1[0][0] = 111</span><br><span class="line">print(list2) # [[111, 456], [789, 213]]</span><br><span class="line">print(list3) # [[111, 456], [789, 213]]</span><br><span class="line">[123, 456, 789, 213]</span><br><span class="line">[123, 456, 789, 213]</span><br><span class="line">[123, 213, 456, 789]</span><br><span class="line">[123, 456, 789, 213]</span><br><span class="line">[[123, 456], [789, 213]]</span><br><span class="line">[[123, 456], [789, 213]]</span><br><span class="line">[[111, 456], [789, 213]]</span><br><span class="line">[[111, 456], [789, 213]]</span><br></pre></td></tr></table></figure><h2 id="6-列表的常用操作符"><a href="#6-列表的常用操作符" class="headerlink" title="6. 列表的常用操作符"></a>6. 列表的常用操作符</h2><ul><li>等号操作符：<code>==</code></li><li>连接操作符 <code>+</code></li><li>重复操作符 <code>*</code></li><li>成员关系操作符 <code>in</code>、<code>not in</code></li></ul><p>「等号 ==」，只有成员、成员位置都相同时才返回True。</p><p>列表拼接有两种方式，用「加号 +」和「乘号 *」，前者首尾拼接，后者复制拼接。</p><p>【例子】</p><p>[21]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line">list1 = [123, 456]</span><br><span class="line">list2 = [456, 123]</span><br><span class="line">list3 = [123, 456]</span><br><span class="line"></span><br><span class="line">print(list1 == list2) # False</span><br><span class="line">print(list1 == list3) # True</span><br><span class="line"></span><br><span class="line">list4 = list1 + list2 # extend()</span><br><span class="line">print(list4) # [123, 456, 456, 123]</span><br><span class="line"></span><br><span class="line">list5 = list3 * 3</span><br><span class="line">print(list5) # [123, 456, 123, 456, 123, 456]</span><br><span class="line"></span><br><span class="line">list3 *= 3</span><br><span class="line">print(list3) # [123, 456, 123, 456, 123, 456]</span><br><span class="line"></span><br><span class="line">print(123 in list3) # True</span><br><span class="line">print(456 not in list3) # False</span><br><span class="line">False</span><br><span class="line">True</span><br><span class="line">[123, 456, 456, 123]</span><br><span class="line">[123, 456, 123, 456, 123, 456]</span><br><span class="line">[123, 456, 123, 456, 123, 456]</span><br><span class="line">True</span><br><span class="line">False</span><br></pre></td></tr></table></figure><p>前面三种方法（<code>append</code>, <code>extend</code>, <code>insert</code>）可对列表增加元素，它们没有返回值，是直接修改了原数据对象。 而将两个list相加，需要创建新的 list 对象，从而需要消耗额外的内存，特别是当 list 较大时，尽量不要使用 “+” 来添加list。</p><h2 id="7-列表的其它方法"><a href="#7-列表的其它方法" class="headerlink" title="7. 列表的其它方法"></a>7. 列表的其它方法</h2><p><code>list.count(obj)</code> 统计某个元素在列表中出现的次数</p><p>【例子】</p><p>[22]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">list1 = [123, 456] * 3</span><br><span class="line">print(list1) # [123, 456, 123, 456, 123, 456]</span><br><span class="line">num = list1.count(123)</span><br><span class="line">print(num) # 3</span><br><span class="line">[123, 456, 123, 456, 123, 456]</span><br><span class="line">3</span><br></pre></td></tr></table></figure><p><code>list.index(x[, start[, end]])</code> 从列表中找出某个值第一个匹配项的索引位置</p><p>【例子】</p><p>[23]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">list1 = [123, 456] * 5</span><br><span class="line">print(list1.index(123)) # 0</span><br><span class="line">print(list1.index(123, 1)) # 2</span><br><span class="line">print(list1.index(123, 3, 7)) # 4</span><br><span class="line">0</span><br><span class="line">2</span><br><span class="line">4</span><br></pre></td></tr></table></figure><p><code>list.reverse()</code> 反向列表中元素</p><p>【例子】</p><p>[24]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">x = [123, 456, 789]</span><br><span class="line">x.reverse()</span><br><span class="line">print(x) # [789, 456, 123]</span><br><span class="line">[789, 456, 123]</span><br></pre></td></tr></table></figure><p><code>list.sort(key=None, reverse=False)</code> 对原列表进行排序。</p><ul><li><code>key</code> – 主要是用来进行比较的元素，只有一个参数，具体的函数的参数就是取自于可迭代对象中，指定可迭代对象中的一个元素来进行排序。</li><li><code>reverse</code> – 排序规则，<code>reverse = True</code> 降序， <code>reverse = False</code> 升序（默认）。</li><li>该方法没有返回值，但是会对列表的对象进行排序。</li></ul><p>【例子】</p><p>[25]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line">x = [123, 456, 789, 213]</span><br><span class="line">x.sort()</span><br><span class="line">print(x)</span><br><span class="line"># [123, 213, 456, 789]</span><br><span class="line"></span><br><span class="line">x.sort(reverse=True)</span><br><span class="line">print(x)</span><br><span class="line"># [789, 456, 213, 123]</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"># 获取列表的第二个元素</span><br><span class="line">def takeSecond(elem):</span><br><span class="line"> return elem[1]</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">x = [(2, 2), (3, 4), (4, 1), (1, 3)]</span><br><span class="line">x.sort(key=takeSecond)</span><br><span class="line">print(x)</span><br><span class="line"># [(4, 1), (2, 2), (1, 3), (3, 4)]</span><br><span class="line"></span><br><span class="line">x.sort(key=lambda a: a[0])</span><br><span class="line">print(x)</span><br><span class="line"># [(1, 3), (2, 2), (3, 4), (4, 1)]</span><br><span class="line">[123, 213, 456, 789]</span><br><span class="line">[789, 456, 213, 123]</span><br><span class="line">[(4, 1), (2, 2), (1, 3), (3, 4)]</span><br><span class="line">[(1, 3), (2, 2), (3, 4), (4, 1)]</span><br></pre></td></tr></table></figure><h1 id="元组"><a href="#元组" class="headerlink" title="元组"></a>元组</h1><p>「元组」定义语法为：<code>(元素1, 元素2, ..., 元素n)</code></p><ul><li>小括号把所有元素绑在一起</li><li>逗号将每个元素一一分开</li></ul><h2 id="1-创建和访问一个元组"><a href="#1-创建和访问一个元组" class="headerlink" title="1. 创建和访问一个元组"></a>1. 创建和访问一个元组</h2><ul><li>Python 的元组与列表类似，不同之处在于tuple被创建后就不能对其进行修改，类似字符串。</li><li>元组使用小括号，列表使用方括号。</li><li>元组与列表类似，也用整数来对它进行索引 (indexing) 和切片 (slicing)。</li></ul><p>【例子】</p><p>[26]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line">t1 = (1, 10.31, 'python')</span><br><span class="line">t2 = 1, 10.31, 'python'</span><br><span class="line">print(t1, type(t1))</span><br><span class="line"># (1, 10.31, 'python') <class 'tuple'></span><br><span class="line"></span><br><span class="line">print(t2, type(t2))</span><br><span class="line"># (1, 10.31, 'python') <class 'tuple'></span><br><span class="line"></span><br><span class="line">tuple1 = (1, 2, 3, 4, 5, 6, 7, 8)</span><br><span class="line">print(tuple1[1]) # 2</span><br><span class="line">print(tuple1[5:]) # (6, 7, 8)</span><br><span class="line">print(tuple1[:5]) # (1, 2, 3, 4, 5)</span><br><span class="line">tuple2 = tuple1[:]</span><br><span class="line">print(tuple2) # (1, 2, 3, 4, 5, 6, 7, 8)</span><br><span class="line">(1, 10.31, 'python') <class 'tuple'></span><br><span class="line">(1, 10.31, 'python') <class 'tuple'></span><br><span class="line">2</span><br><span class="line">(6, 7, 8)</span><br><span class="line">(1, 2, 3, 4, 5)</span><br><span class="line">(1, 2, 3, 4, 5, 6, 7, 8)</span><br></pre></td></tr></table></figure><ul><li>创建元组可以用小括号 ()，也可以什么都不用，为了可读性，建议还是用 ()。</li><li>元组中只包含一个元素时，需要在元素后面添加逗号，否则括号会被当作运算符使用。</li></ul><p>【例子】</p><p>[27]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">x = (1)</span><br><span class="line">print(type(x)) # <class 'int'></span><br><span class="line">x = 2, 3, 4, 5</span><br><span class="line">print(type(x)) # <class 'tuple'></span><br><span class="line">x = []</span><br><span class="line">print(type(x)) # <class 'list'></span><br><span class="line">x = ()</span><br><span class="line">print(type(x)) # <class 'tuple'></span><br><span class="line">x = (1,)</span><br><span class="line">print(type(x)) # <class 'tuple'></span><br><span class="line"><class 'int'></span><br><span class="line"><class 'tuple'></span><br><span class="line"><class 'list'></span><br><span class="line"><class 'tuple'></span><br><span class="line"><class 'tuple'></span><br></pre></td></tr></table></figure><p>【例子】</p><p>[28]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">print(8 * (8)) # 64</span><br><span class="line">print(8 * (8,)) # (8, 8, 8, 8, 8, 8, 8, 8)</span><br><span class="line">64</span><br><span class="line">(8, 8, 8, 8, 8, 8, 8, 8)</span><br></pre></td></tr></table></figure><p>【例子】创建二维元组。</p><p>[29]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">x = (1, 10.31, 'python'), ('data', 11)</span><br><span class="line">print(x)</span><br><span class="line"># ((1, 10.31, 'python'), ('data', 11))</span><br><span class="line"></span><br><span class="line">print(x[0])</span><br><span class="line"># (1, 10.31, 'python')</span><br><span class="line">print(x[0][0], x[0][1], x[0][2])</span><br><span class="line"># 1 10.31 python</span><br><span class="line"></span><br><span class="line">print(x[0][0:2])</span><br><span class="line"># (1, 10.31)</span><br><span class="line">((1, 10.31, 'python'), ('data', 11))</span><br><span class="line">(1, 10.31, 'python')</span><br><span class="line">1 10.31 python</span><br><span class="line">(1, 10.31)</span><br></pre></td></tr></table></figure><h2 id="2-更新和删除一个元组"><a href="#2-更新和删除一个元组" class="headerlink" title="2. 更新和删除一个元组"></a>2. 更新和删除一个元组</h2><p>【例子】</p><p>[30]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">week = ('Monday', 'Tuesday', 'Thursday', 'Friday')</span><br><span class="line">week = week[:2] + ('Wednesday',) + week[2:]</span><br><span class="line">print(week) # ('Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday')</span><br><span class="line">('Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday')</span><br></pre></td></tr></table></figure><p>【例子】元组有不可更改 (immutable) 的性质，因此不能直接给元组的元素赋值，但是只要元组中的元素可更改 (mutable)，那么我们可以直接更改其元素，注意这跟赋值其元素不同。</p><p>[31]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">t1 = (1, 2, 3, [4, 5, 6])</span><br><span class="line">print(t1) # (1, 2, 3, [4, 5, 6])</span><br><span class="line"></span><br><span class="line">t1[3][0] = 9</span><br><span class="line">print(t1) # (1, 2, 3, [9, 5, 6])</span><br><span class="line">(1, 2, 3, [4, 5, 6])</span><br><span class="line">(1, 2, 3, [9, 5, 6])</span><br></pre></td></tr></table></figure><h2 id="3-元组相关的操作符"><a href="#3-元组相关的操作符" class="headerlink" title="3. 元组相关的操作符"></a>3. 元组相关的操作符</h2><ul><li>等号操作符：<code>==</code></li><li>连接操作符 <code>+</code></li><li>重复操作符 <code>*</code></li><li>成员关系操作符 <code>in</code>、<code>not in</code></li></ul><p>「等号 ==」，只有成员、成员位置都相同时才返回True。</p><p>元组拼接有两种方式，用「加号 +」和「乘号 *」，前者首尾拼接，后者复制拼接。</p><p>【例子】</p><p>[32]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line">t1 = (123, 456)</span><br><span class="line">t2 = (456, 123)</span><br><span class="line">t3 = (123, 456)</span><br><span class="line"></span><br><span class="line">print(t1 == t2) # False</span><br><span class="line">print(t1 == t3) # True</span><br><span class="line"></span><br><span class="line">t4 = t1 + t2</span><br><span class="line">print(t4) # (123, 456, 456, 123)</span><br><span class="line"></span><br><span class="line">t5 = t3 * 3</span><br><span class="line">print(t5) # (123, 456, 123, 456, 123, 456)</span><br><span class="line"></span><br><span class="line">t3 *= 3</span><br><span class="line">print(t3) # (123, 456, 123, 456, 123, 456)</span><br><span class="line"></span><br><span class="line">print(123 in t3) # True</span><br><span class="line">print(456 not in t3) # False</span><br><span class="line">False</span><br><span class="line">True</span><br><span class="line">(123, 456, 456, 123)</span><br><span class="line">(123, 456, 123, 456, 123, 456)</span><br><span class="line">(123, 456, 123, 456, 123, 456)</span><br><span class="line">True</span><br><span class="line">False</span><br></pre></td></tr></table></figure><h2 id="4-内置方法"><a href="#4-内置方法" class="headerlink" title="4. 内置方法"></a>4. 内置方法</h2><p>元组大小和内容都不可更改，因此只有 <code>count</code> 和 <code>index</code> 两种方法。</p><p>【例子】</p><p>[33]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">t = (1, 10.31, 'python')</span><br><span class="line">print(t.count('python')) # 1</span><br><span class="line">print(t.index(10.31)) # 1</span><br><span class="line">1</span><br><span class="line">1</span><br></pre></td></tr></table></figure><ul><li><code>count('python')</code> 是记录在元组 <code>t</code> 中该元素出现几次，显然是 1 次</li><li><code>index(10.31)</code> 是找到该元素在元组 <code>t</code> 的索引，显然是 1</li></ul><h2 id="5-解压元组"><a href="#5-解压元组" class="headerlink" title="5. 解压元组"></a>5. 解压元组</h2><p>【例子】解压（unpack）一维元组（有几个元素左边括号定义几个变量）</p><p>[34]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">t = (1, 10.31, 'python')</span><br><span class="line">(a, b, c) = t</span><br><span class="line">print(a, b, c)</span><br><span class="line"># 1 10.31 python</span><br><span class="line">1 10.31 python</span><br></pre></td></tr></table></figure><p>【例子】解压二维元组（按照元组里的元组结构来定义变量）</p><p>[35]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">t = (1, 10.31, ('OK', 'python'))</span><br><span class="line">(a, b, (c, d)) = t</span><br><span class="line">print(a, b, c, d)</span><br><span class="line"># 1 10.31 OK python</span><br><span class="line">1 10.31 OK python</span><br></pre></td></tr></table></figure><p>【例子】如果你只想要元组其中几个元素，用通配符「*」，英文叫 wildcard，在计算机语言中代表一个或多个元素。下例就是把多个元素丢给了 <code>rest</code> 变量。</p><p>[36]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">t = 1, 2, 3, 4, 5</span><br><span class="line">a, b, *rest, c = t</span><br><span class="line">print(a, b, c) # 1 2 5</span><br><span class="line">print(rest) # [3, 4]</span><br><span class="line">1 2 5</span><br><span class="line">[3, 4]</span><br></pre></td></tr></table></figure><p>【例子】如果你根本不在乎 rest 变量，那么就用通配符「*」加上下划线「_」。</p><p>[37]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">t = 1, 2, 3, 4, 5</span><br><span class="line">a, b, *_ = t</span><br><span class="line">print(a, b) # 1 2</span><br><span class="line">1 2</span><br></pre></td></tr></table></figure><h1 id="字符串"><a href="#字符串" class="headerlink" title="字符串"></a>字符串</h1><h2 id="1-字符串的定义"><a href="#1-字符串的定义" class="headerlink" title="1. 字符串的定义"></a>1. 字符串的定义</h2><ul><li>Python 中字符串被定义为引号之间的字符集合。</li><li>Python 支持使用成对的 单引号 或 双引号。</li></ul><p>【例子】</p><p>[38]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">t1 = 'i love Python!'</span><br><span class="line">print(t1, type(t1))</span><br><span class="line"># i love Python! <class 'str'></span><br><span class="line"></span><br><span class="line">t2 = "I love Python!"</span><br><span class="line">print(t2, type(t2))</span><br><span class="line"># I love Python! <class 'str'></span><br><span class="line"></span><br><span class="line">print(5 + 8) # 13</span><br><span class="line">print('5' + '8') # 58</span><br><span class="line">i love Python! <class 'str'></span><br><span class="line">I love Python! <class 'str'></span><br><span class="line">13</span><br><span class="line">58</span><br></pre></td></tr></table></figure><ul><li>Python 的常用转义字符</li></ul><table><thead><tr><th>转义字符</th><th>描述</th></tr></thead><tbody><tr><td><code>\\</code></td><td>反斜杠符号</td></tr><tr><td><code>\'</code></td><td>单引号</td></tr><tr><td><code>\"</code></td><td>双引号</td></tr><tr><td><code>\n</code></td><td>换行</td></tr><tr><td><code>\t</code></td><td>横向制表符(TAB)</td></tr><tr><td><code>\r</code></td><td>回车</td></tr></tbody></table><p>【例子】如果字符串中需要出现单引号或双引号，可以使用转义符号<code>\</code>对字符串中的符号进行转义。</p><p>[39]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">print('let\'s go') # let's go</span><br><span class="line">print("let's go") # let's go</span><br><span class="line">print('C:\\now') # C:\now</span><br><span class="line">print("C:\\Program Files\\Intel\\Wifi\\Help")</span><br><span class="line"># C:\Program Files\Intel\Wifi\Help</span><br><span class="line">let's go</span><br><span class="line">let's go</span><br><span class="line">C:\now</span><br><span class="line">C:\Program Files\Intel\Wifi\Help</span><br></pre></td></tr></table></figure><p>【例子】原始字符串只需要在字符串前边加一个英文字母 r 即可。</p><p>[40]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">print(r'C:\Program Files\Intel\Wifi\Help') </span><br><span class="line"># C:\Program Files\Intel\Wifi\Help</span><br><span class="line">C:\Program Files\Intel\Wifi\Help</span><br></pre></td></tr></table></figure><p>【例子】三引号允许一个字符串跨多行，字符串中可以包含换行符、制表符以及其他特殊字符。</p><p>[41]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><span class="line">para_str = """这是一个多行字符串的实例</span><br><span class="line">多行字符串可以使用制表符</span><br><span class="line">TAB ( \t )。</span><br><span class="line">也可以使用换行符 [ \n ]。</span><br><span class="line">"""</span><br><span class="line">print(para_str)</span><br><span class="line"># 这是一个多行字符串的实例</span><br><span class="line"># 多行字符串可以使用制表符</span><br><span class="line"># TAB ( )。</span><br><span class="line"># 也可以使用换行符 [</span><br><span class="line"># ]。</span><br><span class="line"></span><br><span class="line">para_str = '''这是一个多行字符串的实例</span><br><span class="line">多行字符串可以使用制表符</span><br><span class="line">TAB ( \t )。</span><br><span class="line">也可以使用换行符 [ \n ]。</span><br><span class="line">'''</span><br><span class="line">print(para_str)</span><br><span class="line"># 这是一个多行字符串的实例</span><br><span class="line"># 多行字符串可以使用制表符</span><br><span class="line"># TAB ( )。</span><br><span class="line"># 也可以使用换行符 [ </span><br><span class="line"># ]。</span><br><span class="line">这是一个多行字符串的实例</span><br><span class="line">多行字符串可以使用制表符</span><br><span class="line">TAB ( )。</span><br><span class="line">也可以使用换行符 [ </span><br><span class="line"> ]。</span><br><span class="line"></span><br><span class="line">这是一个多行字符串的实例</span><br><span class="line">多行字符串可以使用制表符</span><br><span class="line">TAB ( )。</span><br><span class="line">也可以使用换行符 [ </span><br><span class="line"> ]。</span><br></pre></td></tr></table></figure><h2 id="2-字符串的切片与拼接"><a href="#2-字符串的切片与拼接" class="headerlink" title="2. 字符串的切片与拼接"></a>2. 字符串的切片与拼接</h2><ul><li>类似于元组具有不可修改性</li><li>从 0 开始 (和 Java 一样)</li><li>切片通常写成 <code>start:end</code> 这种形式，包括「<code>start</code> 索引」对应的元素，不包括「<code>end</code>索引」对应的元素。</li><li>索引值可正可负，正索引从 0 开始，从左往右；负索引从 -1 开始，从右往左。使用负数索引时，会从最后一个元素开始计数。最后一个元素的位置编号是 -1。</li></ul><p>【例子】</p><p>[42]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line">str1 = 'I Love LsgoGroup'</span><br><span class="line">print(str1[:6]) # I Love</span><br><span class="line">print(str1[5]) # e</span><br><span class="line">print(str1[:6] + " 插入的字符串 " + str1[6:]) </span><br><span class="line"># I Love 插入的字符串 LsgoGroup</span><br><span class="line"></span><br><span class="line">s = 'Python'</span><br><span class="line">print(s) # Python</span><br><span class="line">print(s[2:4]) # th</span><br><span class="line">print(s[-5:-2]) # yth</span><br><span class="line">print(s[2]) # t</span><br><span class="line">print(s[-1]) # n</span><br><span class="line">I Love</span><br><span class="line">e</span><br><span class="line">I Love 插入的字符串 LsgoGroup</span><br><span class="line">Python</span><br><span class="line">th</span><br><span class="line">yth</span><br><span class="line">t</span><br><span class="line">n</span><br></pre></td></tr></table></figure><h2 id="3-字符串的常用内置方法"><a href="#3-字符串的常用内置方法" class="headerlink" title="3. 字符串的常用内置方法"></a>3. 字符串的常用内置方法</h2><ul><li><code>capitalize()</code> 将字符串的第一个字符转换为大写。</li></ul><p>【例子】</p><p>[43]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">str2 = 'xiaoxie'</span><br><span class="line">print(str2.capitalize()) # Xiaoxie</span><br><span class="line">Xiaoxie</span><br></pre></td></tr></table></figure><ul><li><code>lower()</code> 转换字符串中所有大写字符为小写。</li><li><code>upper()</code> 转换字符串中的小写字母为大写。</li><li><code>swapcase()</code> 将字符串中大写转换为小写，小写转换为大写。</li></ul><p>【例子】</p><p>[44]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">str2 = "DAXIExiaoxie"</span><br><span class="line">print(str2.lower()) # daxiexiaoxie</span><br><span class="line">print(str2.upper()) # DAXIEXIAOXIE</span><br><span class="line">print(str2.swapcase()) # daxieXIAOXIE</span><br><span class="line">daxiexiaoxie</span><br><span class="line">DAXIEXIAOXIE</span><br><span class="line">daxieXIAOXIE</span><br></pre></td></tr></table></figure><ul><li><code>count(str, beg= 0,end=len(string))</code> 返回<code>str</code>在 string 里面出现的次数，如果<code>beg</code>或者<code>end</code>指定则返回指定范围内<code>str</code>出现的次数。</li></ul><p>【例子】</p><p>[45]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">str2 = "DAXIExiaoxie"</span><br><span class="line">print(str2.count('xi')) # 2</span><br><span class="line">2</span><br></pre></td></tr></table></figure><ul><li><code>endswith(suffix, beg=0, end=len(string))</code> 检查字符串是否以指定子字符串 <code>suffix</code> 结束，如果是，返回 True，否则返回 False。如果 <code>beg</code> 和 <code>end</code> 指定值，则在指定范围内检查。</li><li><code>startswith(substr, beg=0,end=len(string))</code> 检查字符串是否以指定子字符串 <code>substr</code> 开头，如果是，返回 True，否则返回 False。如果 <code>beg</code> 和 <code>end</code> 指定值，则在指定范围内检查。</li></ul><p>【例子】</p><p>[46]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">str2 = "DAXIExiaoxie"</span><br><span class="line">print(str2.endswith('ie')) # True</span><br><span class="line">print(str2.endswith('xi')) # False</span><br><span class="line">print(str2.startswith('Da')) # False</span><br><span class="line">print(str2.startswith('DA')) # True</span><br><span class="line">True</span><br><span class="line">False</span><br><span class="line">False</span><br><span class="line">True</span><br></pre></td></tr></table></figure><ul><li><code>find(str, beg=0, end=len(string))</code> 检测 <code>str</code> 是否包含在字符串中，如果指定范围 <code>beg</code> 和 <code>end</code>，则检查是否包含在指定范围内，如果包含，返回开始的索引值，否则返回 -1。</li><li><code>rfind(str, beg=0,end=len(string))</code> 类似于 <code>find()</code> 函数，不过是从右边开始查找。</li></ul><p>【例子】</p><p>[47]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">str2 = "DAXIExiaoxie"</span><br><span class="line">print(str2.find('xi')) # 5</span><br><span class="line">print(str2.find('ix')) # -1</span><br><span class="line">print(str2.rfind('xi')) # 9</span><br><span class="line">5</span><br><span class="line">-1</span><br><span class="line">9</span><br></pre></td></tr></table></figure><ul><li><code>isnumeric()</code> 如果字符串中只包含数字字符，则返回 True，否则返回 False。</li></ul><p>【例子】</p><p>[48]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">str3 = '12345'</span><br><span class="line">print(str3.isnumeric()) # True</span><br><span class="line">str3 += 'a'</span><br><span class="line">print(str3.isnumeric()) # False</span><br><span class="line">True</span><br><span class="line">False</span><br></pre></td></tr></table></figure><ul><li><code>ljust(width[, fillchar])</code>返回一个原字符串左对齐，并使用<code>fillchar</code>（默认空格）填充至长度<code>width</code>的新字符串。</li><li><code>rjust(width[, fillchar])</code>返回一个原字符串右对齐，并使用<code>fillchar</code>（默认空格）填充至长度<code>width</code>的新字符串。</li></ul><p>【例子】</p><p>[49]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">str4 = '1101'</span><br><span class="line">print(str4.ljust(8, '0')) # 11010000</span><br><span class="line">print(str4.rjust(8, '0')) # 00001101</span><br><span class="line">11010000</span><br><span class="line">00001101</span><br></pre></td></tr></table></figure><ul><li><code>lstrip([chars])</code> 截掉字符串左边的空格或指定字符。</li><li><code>rstrip([chars])</code> 删除字符串末尾的空格或指定字符。</li><li><code>strip([chars])</code> 在字符串上执行<code>lstrip()</code>和<code>rstrip()</code>。</li></ul><p>【例子】</p><p>[50]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">str5 = ' I Love LsgoGroup '</span><br><span class="line">print(str5.lstrip()) # 'I Love LsgoGroup '</span><br><span class="line">print(str5.lstrip().strip('I')) # ' Love LsgoGroup '</span><br><span class="line">print(str5.rstrip()) # ' I Love LsgoGroup'</span><br><span class="line">print(str5.strip()) # 'I Love LsgoGroup'</span><br><span class="line">print(str5.strip().strip('p')) # 'I Love LsgoGrou'</span><br><span class="line">I Love LsgoGroup </span><br><span class="line"> Love LsgoGroup </span><br><span class="line"> I Love LsgoGroup</span><br><span class="line">I Love LsgoGroup</span><br><span class="line">I Love LsgoGrou</span><br></pre></td></tr></table></figure><ul><li><code>partition(sub)</code> 找到子字符串sub，把字符串分为一个三元组<code>(pre_sub,sub,fol_sub)</code>，如果字符串中不包含sub则返回<code>('原字符串','','')</code>。</li><li><code>rpartition(sub)</code>类似于<code>partition()</code>方法，不过是从右边开始查找。</li></ul><p>【例子】</p><p>[51]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">str5 = ' I Love LsgoGroup '</span><br><span class="line">print(str5.strip().partition('o')) # ('I L', 'o', 've LsgoGroup')</span><br><span class="line">print(str5.strip().partition('m')) # ('I Love LsgoGroup', '', '')</span><br><span class="line">print(str5.strip().rpartition('o')) # ('I Love LsgoGr', 'o', 'up')</span><br><span class="line">('I L', 'o', 've LsgoGroup')</span><br><span class="line">('I Love LsgoGroup', '', '')</span><br><span class="line">('I Love LsgoGr', 'o', 'up')</span><br></pre></td></tr></table></figure><ul><li><code>replace(old, new [, max])</code> 把 将字符串中的<code>old</code>替换成<code>new</code>，如果<code>max</code>指定，则替换不超过<code>max</code>次。</li></ul><p>【例子】</p><p>[52]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">str5 = ' I Love LsgoGroup '</span><br><span class="line">print(str5.strip().replace('I', 'We')) # We Love LsgoGroup</span><br><span class="line">We Love LsgoGroup</span><br></pre></td></tr></table></figure><ul><li><code>split(str="", num)</code> 不带参数默认是以空格为分隔符切片字符串，如果<code>num</code>参数有设置，则仅分隔<code>num</code>个子字符串，返回切片后的子字符串拼接的列表。</li></ul><p>【例子】</p><p>[53]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">str5 = ' I Love LsgoGroup '</span><br><span class="line">print(str5.strip().split()) # ['I', 'Love', 'LsgoGroup']</span><br><span class="line">print(str5.strip().split('o')) # ['I L', 've Lsg', 'Gr', 'up']</span><br><span class="line">['I', 'Love', 'LsgoGroup']</span><br><span class="line">['I L', 've Lsg', 'Gr', 'up']</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[54]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br></pre></td><td class="code"><pre><span class="line">u = "www.baidu.com.cn"</span><br><span class="line"># 使用默认分隔符</span><br><span class="line">print(u.split()) # ['www.baidu.com.cn']</span><br><span class="line"></span><br><span class="line"># 以"."为分隔符</span><br><span class="line">print((u.split('.'))) # ['www', 'baidu', 'com', 'cn']</span><br><span class="line"></span><br><span class="line"># 分割0次</span><br><span class="line">print((u.split(".", 0))) # ['www.baidu.com.cn']</span><br><span class="line"></span><br><span class="line"># 分割一次</span><br><span class="line">print((u.split(".", 1))) # ['www', 'baidu.com.cn']</span><br><span class="line"></span><br><span class="line"># 分割两次</span><br><span class="line">print(u.split(".", 2)) # ['www', 'baidu', 'com.cn']</span><br><span class="line"></span><br><span class="line"># 分割两次，并取序列为1的项</span><br><span class="line">print((u.split(".", 2)[1])) # baidu</span><br><span class="line"></span><br><span class="line"># 分割两次，并把分割后的三个部分保存到三个变量</span><br><span class="line">u1, u2, u3 = u.split(".", 2)</span><br><span class="line">print(u1) # www</span><br><span class="line">print(u2) # baidu</span><br><span class="line">print(u3) # com.cn</span><br><span class="line">['www.baidu.com.cn']</span><br><span class="line">['www', 'baidu', 'com', 'cn']</span><br><span class="line">['www.baidu.com.cn']</span><br><span class="line">['www', 'baidu.com.cn']</span><br><span class="line">['www', 'baidu', 'com.cn']</span><br><span class="line">baidu</span><br><span class="line">www</span><br><span class="line">baidu</span><br><span class="line">com.cn</span><br></pre></td></tr></table></figure><p>【例子】去掉换行符</p><p>[55]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">c = '''say</span><br><span class="line">hello</span><br><span class="line">baby'''</span><br><span class="line"></span><br><span class="line">print(c)</span><br><span class="line"># say</span><br><span class="line"># hello</span><br><span class="line"># baby</span><br><span class="line"></span><br><span class="line">print(c.split('\n')) # ['say', 'hello', 'baby']</span><br><span class="line">say</span><br><span class="line">hello</span><br><span class="line">baby</span><br><span class="line">['say', 'hello', 'baby']</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[56]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">string = "hello boy<[www.baidu.com]>byebye"</span><br><span class="line">print(string.split('[')[1].split(']')[0]) # www.baidu.com</span><br><span class="line">print(string.split('[')[1].split(']')[0].split('.')) # ['www', 'baidu', 'com']</span><br><span class="line">www.baidu.com</span><br><span class="line">['www', 'baidu', 'com']</span><br></pre></td></tr></table></figure><ul><li><code>splitlines([keepends])</code> 按照行(‘\r’, ‘\r\n’, \n’)分隔，返回一个包含各行作为元素的列表，如果参数<code>keepends</code>为 False，不包含换行符，如果为 True，则保留换行符。</li></ul><p>【例子】</p><p>[57]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">str6 = 'I \n Love \n LsgoGroup'</span><br><span class="line">print(str6.splitlines()) # ['I ', ' Love ', ' LsgoGroup']</span><br><span class="line">print(str6.splitlines(True)) # ['I \n', ' Love \n', ' LsgoGroup']</span><br><span class="line">['I ', ' Love ', ' LsgoGroup']</span><br><span class="line">['I \n', ' Love \n', ' LsgoGroup']</span><br></pre></td></tr></table></figure><ul><li><code>maketrans(intab, outtab)</code> 创建字符映射的转换表，第一个参数是字符串，表示需要转换的字符，第二个参数也是字符串表示转换的目标。</li><li><code>translate(table, deletechars="")</code> 根据参数<code>table</code>给出的表，转换字符串的字符，要过滤掉的字符放到<code>deletechars</code>参数中。</li></ul><p>【例子】</p><p>[58]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">str7 = 'this is string example....wow!!!'</span><br><span class="line">intab = 'aeiou'</span><br><span class="line">outtab = '12345'</span><br><span class="line">trantab = str7.maketrans(intab, outtab)</span><br><span class="line">print(trantab) # {97: 49, 111: 52, 117: 53, 101: 50, 105: 51}</span><br><span class="line">print(str7.translate(trantab)) # th3s 3s str3ng 2x1mpl2....w4w!!!</span><br><span class="line">{97: 49, 101: 50, 105: 51, 111: 52, 117: 53}</span><br><span class="line">th3s 3s str3ng 2x1mpl2....w4w!!!</span><br></pre></td></tr></table></figure><h2 id="4-字符串格式化"><a href="#4-字符串格式化" class="headerlink" title="4. 字符串格式化"></a>4. 字符串格式化</h2><ul><li><code>format</code> 格式化函数</li></ul><p>【例子】</p><p>[59]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">str8 = "{0} Love {1}".format('I', 'Lsgogroup') # 位置参数</span><br><span class="line">print(str8) # I Love Lsgogroup</span><br><span class="line"></span><br><span class="line">str8 = "{a} Love {b}".format(a='I', b='Lsgogroup') # 关键字参数</span><br><span class="line">print(str8) # I Love Lsgogroup</span><br><span class="line"></span><br><span class="line">str8 = "{0} Love {b}".format('I', b='Lsgogroup') # 位置参数要在关键字参数之前</span><br><span class="line">print(str8) # I Love Lsgogroup</span><br><span class="line"></span><br><span class="line">str8 = '{0:.2f}{1}'.format(27.658, 'GB') # 保留小数点后两位</span><br><span class="line">print(str8) # 27.66GB</span><br><span class="line">I Love Lsgogroup</span><br><span class="line">I Love Lsgogroup</span><br><span class="line">I Love Lsgogroup</span><br><span class="line">27.66GB</span><br></pre></td></tr></table></figure><ul><li>Python 字符串格式化符号</li></ul><table><thead><tr><th>符 号</th><th>描述</th></tr></thead><tbody><tr><td>%c</td><td>格式化字符及其ASCII码</td></tr><tr><td>%s</td><td>格式化字符串，用str()方法处理对象</td></tr><tr><td>%r</td><td>格式化字符串，用rper()方法处理对象</td></tr><tr><td>%d</td><td>格式化整数</td></tr><tr><td>%o</td><td>格式化无符号八进制数</td></tr><tr><td>%x</td><td>格式化无符号十六进制数</td></tr><tr><td>%X</td><td>格式化无符号十六进制数（大写）</td></tr><tr><td>%f</td><td>格式化浮点数字，可指定小数点后的精度</td></tr><tr><td>%e</td><td>用科学计数法格式化浮点数</td></tr><tr><td>%E</td><td>作用同%e，用科学计数法格式化浮点数</td></tr><tr><td>%g</td><td>根据值的大小决定使用%f或%e</td></tr><tr><td>%G</td><td>作用同%g，根据值的大小决定使用%f或%E</td></tr></tbody></table><p>【例子】</p><p>[60]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line">print('%c' % 97) # a</span><br><span class="line">print('%c %c %c' % (97, 98, 99)) # a b c</span><br><span class="line">print('%d + %d = %d' % (4, 5, 9)) # 4 + 5 = 9</span><br><span class="line">print("我叫 %s 今年 %d 岁!" % ('小明', 10)) # 我叫 小明 今年 10 岁!</span><br><span class="line">print('%o' % 10) # 12</span><br><span class="line">print('%x' % 10) # a</span><br><span class="line">print('%X' % 10) # A</span><br><span class="line">print('%f' % 27.658) # 27.658000</span><br><span class="line">print('%e' % 27.658) # 2.765800e+01</span><br><span class="line">print('%E' % 27.658) # 2.765800E+01</span><br><span class="line">print('%g' % 27.658) # 27.658</span><br><span class="line">text = "I am %d years old." % 22</span><br><span class="line">print("I said: %s." % text) # I said: I am 22 years old..</span><br><span class="line">print("I said: %r." % text) # I said: 'I am 22 years old.'</span><br><span class="line">a</span><br><span class="line">a b c</span><br><span class="line">4 + 5 = 9</span><br><span class="line">我叫 小明 今年 10 岁!</span><br><span class="line">12</span><br><span class="line">a</span><br><span class="line">A</span><br><span class="line">27.658000</span><br><span class="line">2.765800e+01</span><br><span class="line">2.765800E+01</span><br><span class="line">27.658</span><br><span class="line">I said: I am 22 years old..</span><br><span class="line">I said: 'I am 22 years old.'.</span><br></pre></td></tr></table></figure><ul><li>格式化操作符辅助指令</li></ul><table><thead><tr><th>符号</th><th>功能</th></tr></thead><tbody><tr><td><code>m.n</code></td><td>m 是显示的最小总宽度,n 是小数点后的位数（如果可用的话）</td></tr><tr><td><code>-</code></td><td>用作左对齐</td></tr><tr><td><code>+</code></td><td>在正数前面显示加号( + )</td></tr><tr><td><code>#</code></td><td>在八进制数前面显示零(‘0’)，在十六进制前面显示’0x’或者’0X’(取决于用的是’x’还是’X’)</td></tr><tr><td><code>0</code></td><td>显示的数字前面填充’0’而不是默认的空格</td></tr></tbody></table><p>【例子】</p><p>[61]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line">print('%5.1f' % 27.658) # ' 27.7'</span><br><span class="line">print('%.2e' % 27.658) # 2.77e+01</span><br><span class="line">print('%10d' % 10) # ' 10'</span><br><span class="line">print('%-10d' % 10) # '10 '</span><br><span class="line">print('%+d' % 10) # +10</span><br><span class="line">print('%#o' % 10) # 0o12</span><br><span class="line">print('%#x' % 108) # 0x6c</span><br><span class="line">print('%010d' % 5) # 0000000005</span><br><span class="line"> 27.7</span><br><span class="line">2.77e+01</span><br><span class="line"> 10</span><br><span class="line">10 </span><br><span class="line">+10</span><br><span class="line">0o12</span><br><span class="line">0x6c</span><br><span class="line">0000000005</span><br></pre></td></tr></table></figure><h1 id="字典"><a href="#字典" class="headerlink" title="字典"></a>字典</h1><h2 id="1-可变类型与不可变类型"><a href="#1-可变类型与不可变类型" class="headerlink" title="1. 可变类型与不可变类型"></a>1. 可变类型与不可变类型</h2><ul><li>序列是以连续的整数为索引，与此不同的是，字典以”关键字”为索引，关键字可以是任意不可变类型，通常用字符串或数值。</li><li>字典是 Python 唯一的一个 映射类型，字符串、元组、列表属于序列类型。</li></ul><p>那么如何快速判断一个数据类型 <code>X</code> 是不是可变类型的呢？两种方法：</p><ul><li>麻烦方法：用 <code>id(X)</code> 函数，对 X 进行某种操作，比较操作前后的 <code>id</code>，如果不一样，则 <code>X</code> 不可变，如果一样，则 <code>X</code> 可变。</li><li>便捷方法：用 <code>hash(X)</code>，只要不报错，证明 <code>X</code> 可被哈希，即不可变，反过来不可被哈希，即可变。</li></ul><p>【例子】</p><p>[62]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">i = 1</span><br><span class="line">print(id(i)) # 140732167000896</span><br><span class="line">i = i + 2</span><br><span class="line">print(id(i)) # 140732167000960</span><br><span class="line"></span><br><span class="line">l = [1, 2]</span><br><span class="line">print(id(l)) # 4300825160</span><br><span class="line">l.append('Python')</span><br><span class="line">print(id(l)) # 4300825160</span><br><span class="line">140731832701760</span><br><span class="line">140731832701824</span><br><span class="line">2131670369800</span><br><span class="line">2131670369800</span><br></pre></td></tr></table></figure><ul><li>整数 <code>i</code> 在加 1 之后的 <code>id</code> 和之前不一样，因此加完之后的这个 <code>i</code> (虽然名字没变)，但不是加之前的那个 <code>i</code> 了，因此整数是不可变类型。</li><li>列表 <code>l</code> 在附加 <code>'Python'</code> 之后的 <code>id</code> 和之前一样，因此列表是可变类型。</li></ul><p>【例子】</p><p>[1]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line">print(hash('Name')) # 7047218704141848153</span><br><span class="line"></span><br><span class="line">print(hash((1, 2, 'Python'))) # 1704535747474881831</span><br><span class="line"></span><br><span class="line">print(hash([1, 2, 'Python']))</span><br><span class="line"># TypeError: unhashable type: 'list'</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">-6668157630988609386</span><br><span class="line">-1857436431894091236</span><br><span class="line">---------------------------------------------------------------------------</span><br><span class="line">TypeError Traceback (most recent call last)</span><br><span class="line"><ipython-input-1-6416367464f8> in <module>()</span><br><span class="line"> 3 print(hash((1, 2, 'Python'))) # 1704535747474881831</span><br><span class="line"> 4 </span><br><span class="line">----> 5 print(hash([1, 2, 'Python']))</span><br><span class="line"> 6 # TypeError: unhashable type: 'list'</span><br><span class="line"></span><br><span class="line">TypeError: unhashable type: 'list'</span><br></pre></td></tr></table></figure><p>[ ]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">print(hash({1, 2, 3}))</span><br><span class="line"># TypeError: unhashable type: 'set'</span><br></pre></td></tr></table></figure><ul><li>数值、字符和元组 都能被哈希，因此它们是不可变类型。</li><li>列表、集合、字典不能被哈希，因此它是可变类型。</li></ul><h2 id="2-字典的定义"><a href="#2-字典的定义" class="headerlink" title="2. 字典的定义"></a>2. 字典的定义</h2><p>字典 是无序的 键:值（<code>key:value</code>）对集合，键必须是互不相同的（在同一个字典之内）。</p><ul><li><code>dict</code> 内部存放的顺序和 <code>key</code> 放入的顺序是没有关系的。</li><li><code>dict</code> 查找和插入的速度极快，不会随着 <code>key</code> 的增加而增加，但是需要占用大量的内存。</li></ul><p>字典 定义语法为 <code>{元素1, 元素2, ..., 元素n}</code></p><ul><li>其中每一个元素是一个「键值对」– 键:值 (<code>key:value</code>)</li><li>关键点是「大括号 {}」,「逗号 ,」和「冒号 :」</li><li>大括号 – 把所有元素绑在一起</li><li>逗号 – 将每个键值对分开</li><li>冒号 – 将键和值分开</li></ul><h2 id="3-创建和访问字典"><a href="#3-创建和访问字典" class="headerlink" title="3. 创建和访问字典"></a>3. 创建和访问字典</h2><p>【例子】</p><p>[88]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">brand = ['李宁', '耐克', '阿迪达斯']</span><br><span class="line">slogan = ['一切皆有可能', 'Just do it', 'Impossible is nothing']</span><br><span class="line">print('耐克的口号是:', slogan[brand.index('耐克')]) </span><br><span class="line"># 耐克的口号是: Just do it</span><br><span class="line"></span><br><span class="line">dic = {'李宁': '一切皆有可能', '耐克': 'Just do it', '阿迪达斯': 'Impossible is nothing'}</span><br><span class="line">print('耐克的口号是:', dic['耐克']) </span><br><span class="line"># 耐克的口号是: Just do it</span><br><span class="line">耐克的口号是: Just do it</span><br><span class="line">耐克的口号是: Just do it</span><br></pre></td></tr></table></figure><p>【例子】通过字符串或数值作为<code>key</code>来创建字典。</p><p>[2]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">dic1 = {1: 'one', 2: 'two', 3: 'three'}</span><br><span class="line">print(dic1) # {1: 'one', 2: 'two', 3: 'three'}</span><br><span class="line">print(dic1[1]) # one</span><br><span class="line">print(dic1[4]) # KeyError: 4</span><br><span class="line"></span><br><span class="line">{1: 'one', 2: 'two', 3: 'three'}</span><br><span class="line">one</span><br><span class="line">---------------------------------------------------------------------------</span><br><span class="line">KeyError Traceback (most recent call last)</span><br><span class="line"><ipython-input-2-bb8d02bd63a3> in <module>()</span><br><span class="line"> 2 print(dic1) # {1: 'one', 2: 'two', 3: 'three'}</span><br><span class="line"> 3 print(dic1[1]) # one</span><br><span class="line">----> 4 print(dic1[4]) # KeyError: 4</span><br><span class="line"></span><br><span class="line">KeyError: 4</span><br></pre></td></tr></table></figure><p>[3]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">dic2 = {'rice': 35, 'wheat': 101, 'corn': 67}</span><br><span class="line">print(dic2) # {'wheat': 101, 'corn': 67, 'rice': 35}</span><br><span class="line">print(dic2['rice']) # 35</span><br><span class="line">{'rice': 35, 'wheat': 101, 'corn': 67}</span><br><span class="line">35</span><br></pre></td></tr></table></figure><p>注意：如果我们取的键在字典中不存在，会直接报错<code>KeyError</code>。</p><p>【例子】通过元组作为<code>key</code>来创建字典，但一般不这样使用。</p><p>[91]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">dic = {(1, 2, 3): "Tom", "Age": 12, 3: [3, 5, 7]}</span><br><span class="line">print(dic) # {(1, 2, 3): 'Tom', 'Age': 12, 3: [3, 5, 7]}</span><br><span class="line">print(type(dic)) # <class 'dict'></span><br><span class="line">{(1, 2, 3): 'Tom', 'Age': 12, 3: [3, 5, 7]}</span><br><span class="line"><class 'dict'></span><br></pre></td></tr></table></figure><p>通过构造函数<code>dict</code>来创建字典。</p><ul><li><code>dict()</code> 创建一个空的字典。</li></ul><p>【例子】通过<code>key</code>直接把数据放入字典中，但一个<code>key</code>只能对应一个<code>value</code>，多次对一个<code>key</code>放入 <code>value</code>，后面的值会把前面的值冲掉。</p><p>[92]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">dic = dict()</span><br><span class="line">dic['a'] = 1</span><br><span class="line">dic['b'] = 2</span><br><span class="line">dic['c'] = 3</span><br><span class="line"></span><br><span class="line">print(dic)</span><br><span class="line"># {'a': 1, 'b': 2, 'c': 3}</span><br><span class="line"></span><br><span class="line">dic['a'] = 11</span><br><span class="line">print(dic)</span><br><span class="line"># {'a': 11, 'b': 2, 'c': 3}</span><br><span class="line"></span><br><span class="line">dic['d'] = 4</span><br><span class="line">print(dic)</span><br><span class="line"># {'a': 11, 'b': 2, 'c': 3, 'd': 4}</span><br><span class="line">{'a': 1, 'b': 2, 'c': 3}</span><br><span class="line">{'a': 11, 'b': 2, 'c': 3}</span><br><span class="line">{'a': 11, 'b': 2, 'c': 3, 'd': 4}</span><br></pre></td></tr></table></figure><ul><li><code>dict(mapping)</code> new dictionary initialized from a mapping object’s (key, value) pairs</li></ul><p>【例子】</p><p>[95]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">dic1 = dict([('apple', 4139), ('peach', 4127), ('cherry', 4098)])</span><br><span class="line">print(dic1) # {'cherry': 4098, 'apple': 4139, 'peach': 4127}</span><br><span class="line"></span><br><span class="line">dic2 = dict((('apple', 4139), ('peach', 4127), ('cherry', 4098)))</span><br><span class="line">print(dic2) # {'peach': 4127, 'cherry': 4098, 'apple': 4139}</span><br><span class="line">{'apple': 4139, 'peach': 4127, 'cherry': 4098}</span><br><span class="line">{'apple': 4139, 'peach': 4127, 'cherry': 4098}</span><br></pre></td></tr></table></figure><ul><li><code>dict(**kwargs)</code> -> new dictionary initialized with the name=value pairs in the keyword argument list. For example: dict(one=1, two=2)</li></ul><p>【例子】这种情况下，键只能为字符串类型，并且创建的时候字符串不能加引号，加上就会直接报语法错误。</p><p>[96]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">dic = dict(name='Tom', age=10)</span><br><span class="line">print(dic) # {'name': 'Tom', 'age': 10}</span><br><span class="line">print(type(dic)) # <class 'dict'></span><br><span class="line">{'name': 'Tom', 'age': 10}</span><br><span class="line"><class 'dict'></span><br></pre></td></tr></table></figure><h2 id="4-字典的内置方法"><a href="#4-字典的内置方法" class="headerlink" title="4. 字典的内置方法"></a>4. 字典的内置方法</h2><ul><li><code>dict.fromkeys(seq[, value])</code> 用于创建一个新字典，以序列 <code>seq</code> 中元素做字典的键，<code>value</code> 为字典所有键对应的初始值。</li></ul><p>【例子】</p><p>[97]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">seq = ('name', 'age', 'sex')</span><br><span class="line">dic1 = dict.fromkeys(seq)</span><br><span class="line">print(dic1)</span><br><span class="line"># {'name': None, 'age': None, 'sex': None}</span><br><span class="line"></span><br><span class="line">dic2 = dict.fromkeys(seq, 10)</span><br><span class="line">print(dic2)</span><br><span class="line"># {'name': 10, 'age': 10, 'sex': 10}</span><br><span class="line"></span><br><span class="line">dic3 = dict.fromkeys(seq, ('小马', '8', '男'))</span><br><span class="line">print(dic3)</span><br><span class="line"># {'name': ('小马', '8', '男'), 'age': ('小马', '8', '男'), 'sex': ('小马', '8', '男')}</span><br><span class="line">{'name': None, 'age': None, 'sex': None}</span><br><span class="line">{'name': 10, 'age': 10, 'sex': 10}</span><br><span class="line">{'name': ('小马', '8', '男'), 'age': ('小马', '8', '男'), 'sex': ('小马', '8', '男')}</span><br></pre></td></tr></table></figure><ul><li><code>dict.keys()</code>返回一个可迭代对象，可以使用 <code>list()</code> 来转换为列表，列表为字典中的所有键。</li></ul><p>【例子】</p><p>[98]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">dic = {'Name': 'lsgogroup', 'Age': 7}</span><br><span class="line">print(dic.keys()) # dict_keys(['Name', 'Age'])</span><br><span class="line">lst = list(dic.keys()) # 转换为列表</span><br><span class="line">print(lst) # ['Name', 'Age']</span><br><span class="line">dict_keys(['Name', 'Age'])</span><br><span class="line">['Name', 'Age']</span><br></pre></td></tr></table></figure><ul><li><code>dict.values()</code>返回一个迭代器，可以使用 <code>list()</code> 来转换为列表，列表为字典中的所有值。</li></ul><p>【例子】</p><p>[100]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">dic = {'Sex': 'female', 'Age': 7, 'Name': 'Zara'}</span><br><span class="line">print(dic.values())</span><br><span class="line"># dict_values(['female', 7, 'Zara'])</span><br><span class="line"></span><br><span class="line">print(list(dic.values()))</span><br><span class="line"># [7, 'female', 'Zara']</span><br><span class="line">dict_values(['female', 7, 'Zara'])</span><br><span class="line">['female', 7, 'Zara']</span><br></pre></td></tr></table></figure><ul><li><code>dict.items()</code>以列表返回可遍历的 (键, 值) 元组数组。</li></ul><p>【例子】</p><p>[101]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">dic = {'Name': 'Lsgogroup', 'Age': 7}</span><br><span class="line">print(dic.items())</span><br><span class="line"># dict_items([('Name', 'Lsgogroup'), ('Age', 7)])</span><br><span class="line"></span><br><span class="line">print(tuple(dic.items()))</span><br><span class="line"># (('Name', 'Lsgogroup'), ('Age', 7))</span><br><span class="line"></span><br><span class="line">print(list(dic.items()))</span><br><span class="line"># [('Name', 'Lsgogroup'), ('Age', 7)]</span><br><span class="line">dict_items([('Name', 'Lsgogroup'), ('Age', 7)])</span><br><span class="line">(('Name', 'Lsgogroup'), ('Age', 7))</span><br><span class="line">[('Name', 'Lsgogroup'), ('Age', 7)]</span><br></pre></td></tr></table></figure><ul><li><code>dict.get(key, default=None)</code> 返回指定键的值，如果值不在字典中返回默认值。</li></ul><p>【例子】</p><p>[102]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">dic = {'Name': 'Lsgogroup', 'Age': 27}</span><br><span class="line">print("Age 值为 : %s" % dic.get('Age')) # Age 值为 : 27</span><br><span class="line">print("Sex 值为 : %s" % dic.get('Sex', "NA")) # Sex 值为 : NA</span><br><span class="line">print(dic) # {'Name': 'Lsgogroup', 'Age': 27}</span><br><span class="line">Age 值为 : 27</span><br><span class="line">Sex 值为 : NA</span><br><span class="line">{'Name': 'Lsgogroup', 'Age': 27}</span><br></pre></td></tr></table></figure><ul><li><code>dict.setdefault(key, default=None)</code>和<code>get()</code>方法 类似, 如果键不存在于字典中，将会添加键并将值设为默认值。</li></ul><p>【例子】</p><p>[103]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">dic = {'Name': 'Lsgogroup', 'Age': 7}</span><br><span class="line">print("Age 键的值为 : %s" % dic.setdefault('Age', None)) # Age 键的值为 : 7</span><br><span class="line">print("Sex 键的值为 : %s" % dic.setdefault('Sex', None)) # Sex 键的值为 : None</span><br><span class="line">print(dic) </span><br><span class="line"># {'Age': 7, 'Name': 'Lsgogroup', 'Sex': None}</span><br><span class="line">Age 键的值为 : 7</span><br><span class="line">Sex 键的值为 : None</span><br><span class="line">{'Name': 'Lsgogroup', 'Age': 7, 'Sex': None}</span><br></pre></td></tr></table></figure><ul><li><code>key in dict</code> <code>in</code> 操作符用于判断键是否存在于字典中，如果键在字典 dict 里返回<code>true</code>，否则返回<code>false</code>。而<code>not in</code>操作符刚好相反，如果键在字典 dict 里返回<code>false</code>，否则返回<code>true</code>。</li></ul><p>【例子】</p><p>[104]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line">dic = {'Name': 'Lsgogroup', 'Age': 7}</span><br><span class="line"></span><br><span class="line"># in 检测键 Age 是否存在</span><br><span class="line">if 'Age' in dic:</span><br><span class="line"> print("键 Age 存在")</span><br><span class="line">else:</span><br><span class="line"> print("键 Age 不存在")</span><br><span class="line"></span><br><span class="line"># 检测键 Sex 是否存在</span><br><span class="line">if 'Sex' in dic:</span><br><span class="line"> print("键 Sex 存在")</span><br><span class="line">else:</span><br><span class="line"> print("键 Sex 不存在")</span><br><span class="line"></span><br><span class="line"># not in 检测键 Age 是否存在</span><br><span class="line">if 'Age' not in dic:</span><br><span class="line"> print("键 Age 不存在")</span><br><span class="line">else:</span><br><span class="line"> print("键 Age 存在")</span><br><span class="line"></span><br><span class="line"># 键 Age 存在</span><br><span class="line"># 键 Sex 不存在</span><br><span class="line"># 键 Age 存在</span><br><span class="line">键 Age 存在</span><br><span class="line">键 Sex 不存在</span><br><span class="line">键 Age 存在</span><br></pre></td></tr></table></figure><ul><li><code>dict.pop(key[,default])</code>删除字典给定键 <code>key</code> 所对应的值，返回值为被删除的值。<code>key</code> 值必须给出。若<code>key</code>不存在，则返回 <code>default</code> 值。</li><li><code>del dict[key]</code> 删除字典给定键 <code>key</code> 所对应的值。</li></ul><p>【例子】</p><p>[105]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">dic1 = {1: "a", 2: [1, 2]}</span><br><span class="line">print(dic1.pop(1), dic1) # a {2: [1, 2]}</span><br><span class="line"></span><br><span class="line"># 设置默认值，必须添加，否则报错</span><br><span class="line">print(dic1.pop(3, "nokey"), dic1) # nokey {2: [1, 2]}</span><br><span class="line"></span><br><span class="line">del dic1[2]</span><br><span class="line">print(dic1) # {}</span><br><span class="line">a {2: [1, 2]}</span><br><span class="line">nokey {2: [1, 2]}</span><br><span class="line">{}</span><br></pre></td></tr></table></figure><ul><li><code>dict.popitem()</code>随机返回并删除字典中的一对键和值，如果字典已经为空，却调用了此方法，就报出KeyError异常。</li></ul><p>【例子】</p><p>[107]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">dic1 = {1: "a", 2: [1, 2]}</span><br><span class="line">print(dic1.popitem()) # {2: [1, 2]}</span><br><span class="line">print(dic1) # (1, 'a')</span><br><span class="line">(2, [1, 2])</span><br><span class="line">{1: 'a'}</span><br></pre></td></tr></table></figure><ul><li><code>dict.clear()</code>用于删除字典内所有元素。</li></ul><p>【例子】</p><p>[108]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">dic = {'Name': 'Zara', 'Age': 7}</span><br><span class="line">print("字典长度 : %d" % len(dic)) # 字典长度 : 2</span><br><span class="line">dic.clear()</span><br><span class="line">print("字典删除后长度 : %d" % len(dic)) </span><br><span class="line"># 字典删除后长度 : 0</span><br><span class="line">字典长度 : 2</span><br><span class="line">字典删除后长度 : 0</span><br></pre></td></tr></table></figure><ul><li><code>dict.copy()</code>返回一个字典的浅复制。</li></ul><p>【例子】</p><p>[109]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">dic1 = {'Name': 'Lsgogroup', 'Age': 7, 'Class': 'First'}</span><br><span class="line">dic2 = dic1.copy()</span><br><span class="line">print("dic2") </span><br><span class="line"># {'Age': 7, 'Name': 'Lsgogroup', 'Class': 'First'}</span><br><span class="line">dic2</span><br></pre></td></tr></table></figure><p>【例子】直接赋值和 copy 的区别</p><p>[110]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line">dic1 = {'user': 'lsgogroup', 'num': [1, 2, 3]}</span><br><span class="line"></span><br><span class="line"># 引用对象</span><br><span class="line">dic2 = dic1 </span><br><span class="line"># 浅拷贝父对象（一级目录），子对象（二级目录）不拷贝，还是引用</span><br><span class="line">dic3 = dic1.copy() </span><br><span class="line"></span><br><span class="line">print(id(dic1)) # 148635574728</span><br><span class="line">print(id(dic2)) # 148635574728</span><br><span class="line">print(id(dic3)) # 148635574344</span><br><span class="line"></span><br><span class="line"># 修改 data 数据</span><br><span class="line">dic1['user'] = 'root'</span><br><span class="line">dic1['num'].remove(1)</span><br><span class="line"></span><br><span class="line"># 输出结果</span><br><span class="line">print(dic1) # {'user': 'root', 'num': [2, 3]}</span><br><span class="line">print(dic2) # {'user': 'root', 'num': [2, 3]}</span><br><span class="line">print(dic3) # {'user': 'runoob', 'num': [2, 3]}</span><br><span class="line">2131669221448</span><br><span class="line">2131669221448</span><br><span class="line">2131669225120</span><br><span class="line">{'user': 'root', 'num': [2, 3]}</span><br><span class="line">{'user': 'root', 'num': [2, 3]}</span><br><span class="line">{'user': 'lsgogroup', 'num': [2, 3]}</span><br></pre></td></tr></table></figure><ul><li><code>dict.update(dict2)</code>把字典参数 <code>dict2</code> 的 <code>key:value</code>对 更新到字典 <code>dict</code> 里。</li></ul><p>【例子】</p><p>[111]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">dic = {'Name': 'Lsgogroup', 'Age': 7}</span><br><span class="line">dic2 = {'Sex': 'female', 'Age': 8}</span><br><span class="line">dic.update(dic2)</span><br><span class="line">print(dic) </span><br><span class="line"># {'Sex': 'female', 'Age': 8, 'Name': 'Lsgogroup'}</span><br><span class="line">{'Name': 'Lsgogroup', 'Age': 8, 'Sex': 'female'}</span><br></pre></td></tr></table></figure><h1 id="集合"><a href="#集合" class="headerlink" title="集合"></a>集合</h1><p>Python 中<code>set</code>与<code>dict</code>类似，也是一组<code>key</code>的集合，但不存储<code>value</code>。由于<code>key</code>不能重复，所以，在<code>set</code>中，没有重复的<code>key</code>。</p><p>注意，<code>key</code>为不可变类型，即可哈希的值。</p><p>【例子】</p><p>[112]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">num = {}</span><br><span class="line">print(type(num)) # <class 'dict'></span><br><span class="line">num = {1, 2, 3, 4}</span><br><span class="line">print(type(num)) # <class 'set'></span><br><span class="line"><class 'dict'></span><br><span class="line"><class 'set'></span><br></pre></td></tr></table></figure><h2 id="1-集合的创建"><a href="#1-集合的创建" class="headerlink" title="1. 集合的创建"></a>1. 集合的创建</h2><ul><li>先创建对象再加入元素。</li><li>在创建空集合的时候只能使用<code>s = set()</code>，因为<code>s = {}</code>创建的是空字典。</li></ul><p>【例子】</p><p>[113]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">basket = set()</span><br><span class="line">basket.add('apple')</span><br><span class="line">basket.add('banana')</span><br><span class="line">print(basket) # {'banana', 'apple'}</span><br><span class="line">{'banana', 'apple'}</span><br></pre></td></tr></table></figure><ul><li>直接把一堆元素用花括号括起来<code>{元素1, 元素2, ..., 元素n}</code>。</li><li>重复元素在<code>set</code>中会被自动被过滤。</li></ul><p>【例子】</p><p>[114]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">basket = {'apple', 'orange', 'apple', 'pear', 'orange', 'banana'}</span><br><span class="line">print(basket) # {'banana', 'apple', 'pear', 'orange'}</span><br><span class="line">{'pear', 'orange', 'banana', 'apple'}</span><br></pre></td></tr></table></figure><ul><li>使用<code>set(value)</code>工厂函数，把列表或元组转换成集合。</li></ul><p>【例子】</p><p>[115]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">a = set('abracadabra')</span><br><span class="line">print(a) </span><br><span class="line"># {'r', 'b', 'd', 'c', 'a'}</span><br><span class="line"></span><br><span class="line">b = set(("Google", "Lsgogroup", "Taobao", "Taobao"))</span><br><span class="line">print(b) </span><br><span class="line"># {'Taobao', 'Lsgogroup', 'Google'}</span><br><span class="line"></span><br><span class="line">c = set(["Google", "Lsgogroup", "Taobao", "Google"])</span><br><span class="line">print(c) </span><br><span class="line"># {'Taobao', 'Lsgogroup', 'Google'}</span><br><span class="line">{'b', 'r', 'a', 'c', 'd'}</span><br><span class="line">{'Taobao', 'Google', 'Lsgogroup'}</span><br><span class="line">{'Taobao', 'Google', 'Lsgogroup'}</span><br></pre></td></tr></table></figure><p>【例子】去掉列表中重复的元素</p><p>[116]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">lst = [0, 1, 2, 3, 4, 5, 5, 3, 1]</span><br><span class="line"></span><br><span class="line">temp = []</span><br><span class="line">for item in lst:</span><br><span class="line"> if item not in temp:</span><br><span class="line"> temp.append(item)</span><br><span class="line"></span><br><span class="line">print(temp) # [0, 1, 2, 3, 4, 5]</span><br><span class="line"></span><br><span class="line">a = set(lst)</span><br><span class="line">print(list(a)) # [0, 1, 2, 3, 4, 5]</span><br><span class="line">[0, 1, 2, 3, 4, 5]</span><br><span class="line">[0, 1, 2, 3, 4, 5]</span><br></pre></td></tr></table></figure><p>从结果发现集合的两个特点：无序 (unordered) 和唯一 (unique)。</p><p>由于 <code>set</code> 存储的是无序集合，所以我们不可以为集合创建索引或执行切片(slice)操作，也没有键(keys)可用来获取集合中元素的值，但是可以判断一个元素是否在集合中。</p><h2 id="2-访问集合中的值"><a href="#2-访问集合中的值" class="headerlink" title="2. 访问集合中的值"></a>2. 访问集合中的值</h2><ul><li>可以使用<code>len()</code>內建函数得到集合的大小。</li></ul><p>【例子】</p><p>[117]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">s = set(['Google', 'Baidu', 'Taobao'])</span><br><span class="line">print(len(s)) # 3</span><br><span class="line">3</span><br></pre></td></tr></table></figure><ul><li>可以使用<code>for</code>把集合中的数据一个个读取出来。</li></ul><p>【例子】</p><p>[7]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">s = set(['Google', 'Baidu', 'Taobao'])</span><br><span class="line">for item in s:</span><br><span class="line"> print(item)</span><br><span class="line"> </span><br><span class="line"># Baidu</span><br><span class="line"># Google</span><br><span class="line"># Taobao</span><br><span class="line">Baidu</span><br><span class="line">Taobao</span><br><span class="line">Google</span><br></pre></td></tr></table></figure><ul><li>可以通过<code>in</code>或<code>not in</code>判断一个元素是否在集合中已经存在</li></ul><p>【例子】</p><p>[119]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">s = set(['Google', 'Baidu', 'Taobao'])</span><br><span class="line">print('Taobao' in s) # True</span><br><span class="line">print('Facebook' not in s) # True</span><br><span class="line">True</span><br><span class="line">True</span><br></pre></td></tr></table></figure><h2 id="3-集合的内置方法"><a href="#3-集合的内置方法" class="headerlink" title="3. 集合的内置方法"></a>3. 集合的内置方法</h2><ul><li><code>set.add(elmnt)</code>用于给集合添加元素，如果添加的元素在集合中已存在，则不执行任何操作。</li></ul><p>【例子】</p><p>[120]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">fruits = {"apple", "banana", "cherry"}</span><br><span class="line">fruits.add("orange")</span><br><span class="line">print(fruits) </span><br><span class="line"># {'orange', 'cherry', 'banana', 'apple'}</span><br><span class="line"></span><br><span class="line">fruits.add("apple")</span><br><span class="line">print(fruits) </span><br><span class="line"># {'orange', 'cherry', 'banana', 'apple'}</span><br><span class="line">{'cherry', 'orange', 'banana', 'apple'}</span><br><span class="line">{'cherry', 'orange', 'banana', 'apple'}</span><br></pre></td></tr></table></figure><ul><li><code>set.update(set)</code>用于修改当前集合，可以添加新的元素或集合到当前集合中，如果添加的元素在集合中已存在，则该元素只会出现一次，重复的会忽略。</li></ul><p>【例子】</p><p>[121]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">x = {"apple", "banana", "cherry"}</span><br><span class="line">y = {"google", "baidu", "apple"}</span><br><span class="line">x.update(y)</span><br><span class="line">print(x)</span><br><span class="line"># {'cherry', 'banana', 'apple', 'google', 'baidu'}</span><br><span class="line"></span><br><span class="line">y.update(["lsgo", "dreamtech"])</span><br><span class="line">print(y)</span><br><span class="line"># {'lsgo', 'baidu', 'dreamtech', 'apple', 'google'}</span><br><span class="line">{'google', 'banana', 'cherry', 'apple', 'baidu'}</span><br><span class="line">{'apple', 'dreamtech', 'lsgo', 'google', 'baidu'}</span><br></pre></td></tr></table></figure><ul><li><code>set.remove(item)</code> 用于移除集合中的指定元素。如果元素不存在，则会发生错误。</li></ul><p>【例子】</p><p>[122]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">fruits = {"apple", "banana", "cherry"}</span><br><span class="line">fruits.remove("banana")</span><br><span class="line">print(fruits) # {'apple', 'cherry'}</span><br><span class="line">{'cherry', 'apple'}</span><br></pre></td></tr></table></figure><ul><li><code>set.discard(value)</code> 用于移除指定的集合元素。<code>remove()</code> 方法在移除一个不存在的元素时会发生错误，而 <code>discard()</code> 方法不会。</li></ul><p>【例子】</p><p>[123]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">fruits = {"apple", "banana", "cherry"}</span><br><span class="line">fruits.discard("banana")</span><br><span class="line">print(fruits) # {'apple', 'cherry'}</span><br><span class="line">{'cherry', 'apple'}</span><br></pre></td></tr></table></figure><ul><li><code>set.pop()</code> 用于随机移除一个元素。</li></ul><p>【例子】</p><p>[66]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">fruits = {"apple", "banana", "cherry"}</span><br><span class="line">x = fruits.pop()</span><br><span class="line">print(fruits) # {'cherry', 'apple'}</span><br><span class="line">print(x) # banana</span><br><span class="line">{'banana', 'apple'}</span><br><span class="line">cherry</span><br></pre></td></tr></table></figure><p>由于 set 是无序和无重复元素的集合，所以两个或多个 set 可以做数学意义上的集合操作。</p><ul><li><code>set.intersection(set1, set2)</code> 返回两个集合的交集。</li><li><code>set1 & set2</code> 返回两个集合的交集。</li><li><code>set.intersection_update(set1, set2)</code> 交集，在原始的集合上移除不重叠的元素。</li></ul><p>【例子】</p><p>[67]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">a = set('abracadabra')</span><br><span class="line">b = set('alacazam')</span><br><span class="line">print(a) # {'r', 'a', 'c', 'b', 'd'}</span><br><span class="line">print(b) # {'c', 'a', 'l', 'm', 'z'}</span><br><span class="line"></span><br><span class="line">c = a.intersection(b)</span><br><span class="line">print(c) # {'a', 'c'}</span><br><span class="line">print(a & b) # {'c', 'a'}</span><br><span class="line">print(a) # {'a', 'r', 'c', 'b', 'd'}</span><br><span class="line"></span><br><span class="line">a.intersection_update(b)</span><br><span class="line">print(a) # {'a', 'c'}</span><br><span class="line">{'b', 'r', 'a', 'c', 'd'}</span><br><span class="line">{'l', 'a', 'c', 'z', 'm'}</span><br><span class="line">{'a', 'c'}</span><br><span class="line">{'a', 'c'}</span><br><span class="line">{'b', 'r', 'a', 'c', 'd'}</span><br><span class="line">{'a', 'c'}</span><br></pre></td></tr></table></figure><ul><li><code>set.union(set1, set2)</code> 返回两个集合的并集。</li><li><code>set1 | set2</code> 返回两个集合的并集。</li></ul><p>【例子】</p><p>[68]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">a = set('abracadabra')</span><br><span class="line">b = set('alacazam')</span><br><span class="line">print(a) # {'r', 'a', 'c', 'b', 'd'}</span><br><span class="line">print(b) # {'c', 'a', 'l', 'm', 'z'}</span><br><span class="line"></span><br><span class="line">print(a | b) </span><br><span class="line"># {'l', 'd', 'm', 'b', 'a', 'r', 'z', 'c'}</span><br><span class="line"></span><br><span class="line">c = a.union(b)</span><br><span class="line">print(c) </span><br><span class="line"># {'c', 'a', 'd', 'm', 'r', 'b', 'z', 'l'}</span><br><span class="line">{'b', 'r', 'a', 'c', 'd'}</span><br><span class="line">{'l', 'a', 'c', 'z', 'm'}</span><br><span class="line">{'l', 'b', 'r', 'a', 'c', 'z', 'd', 'm'}</span><br><span class="line">{'l', 'b', 'r', 'a', 'c', 'z', 'd', 'm'}</span><br></pre></td></tr></table></figure><ul><li><code>set.difference(set)</code> 返回集合的差集。</li><li><code>set1 - set2</code> 返回集合的差集。</li><li><code>set.difference_update(set)</code> 集合的差集，直接在原来的集合中移除元素，没有返回值。</li></ul><p>【例子】</p><p>[69]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">a = set('abracadabra')</span><br><span class="line">b = set('alacazam')</span><br><span class="line">print(a) # {'r', 'a', 'c', 'b', 'd'}</span><br><span class="line">print(b) # {'c', 'a', 'l', 'm', 'z'}</span><br><span class="line"></span><br><span class="line">c = a.difference(b)</span><br><span class="line">print(c) # {'b', 'd', 'r'}</span><br><span class="line">print(a - b) # {'d', 'b', 'r'}</span><br><span class="line"></span><br><span class="line">print(a) # {'r', 'd', 'c', 'a', 'b'}</span><br><span class="line">a.difference_update(b)</span><br><span class="line">print(a) # {'d', 'r', 'b'}</span><br><span class="line">{'b', 'r', 'a', 'c', 'd'}</span><br><span class="line">{'l', 'a', 'c', 'z', 'm'}</span><br><span class="line">{'d', 'b', 'r'}</span><br><span class="line">{'d', 'b', 'r'}</span><br><span class="line">{'b', 'r', 'a', 'c', 'd'}</span><br><span class="line">{'b', 'r', 'd'}</span><br></pre></td></tr></table></figure><ul><li><code>set.symmetric_difference(set)</code>返回集合的异或。</li><li><code>set1 ^ set2</code> 返回集合的异或。</li><li><code>set.symmetric_difference_update(set)</code>移除当前集合中在另外一个指定集合相同的元素，并将另外一个指定集合中不同的元素插入到当前集合中。</li></ul><p>【例子】</p><p>[70]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">a = set('abracadabra')</span><br><span class="line">b = set('alacazam')</span><br><span class="line">print(a) # {'r', 'a', 'c', 'b', 'd'}</span><br><span class="line">print(b) # {'c', 'a', 'l', 'm', 'z'}</span><br><span class="line"></span><br><span class="line">c = a.symmetric_difference(b)</span><br><span class="line">print(c) # {'m', 'r', 'l', 'b', 'z', 'd'}</span><br><span class="line">print(a ^ b) # {'m', 'r', 'l', 'b', 'z', 'd'}</span><br><span class="line"></span><br><span class="line">print(a) # {'r', 'd', 'c', 'a', 'b'}</span><br><span class="line">a.symmetric_difference_update(b)</span><br><span class="line">print(a) # {'r', 'b', 'm', 'l', 'z', 'd'}</span><br><span class="line">{'b', 'r', 'a', 'c', 'd'}</span><br><span class="line">{'l', 'a', 'c', 'z', 'm'}</span><br><span class="line">{'l', 'b', 'z', 'r', 'd', 'm'}</span><br><span class="line">{'l', 'b', 'z', 'r', 'd', 'm'}</span><br><span class="line">{'b', 'r', 'a', 'c', 'd'}</span><br><span class="line">{'l', 'b', 'r', 'z', 'd', 'm'}</span><br></pre></td></tr></table></figure><ul><li><code>set.issubset(set)</code>判断集合是不是被其他集合包含，如果是则返回 True，否则返回 False。</li><li><code>set1 <= set2</code> 判断集合是不是被其他集合包含，如果是则返回 True，否则返回 False。</li></ul><p>【例子】</p><p>[71]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">x = {"a", "b", "c"}</span><br><span class="line">y = {"f", "e", "d", "c", "b", "a"}</span><br><span class="line">z = x.issubset(y)</span><br><span class="line">print(z) # True</span><br><span class="line">print(x <= y) # True</span><br><span class="line"></span><br><span class="line">x = {"a", "b", "c"}</span><br><span class="line">y = {"f", "e", "d", "c", "b"}</span><br><span class="line">z = x.issubset(y)</span><br><span class="line">print(z) # False</span><br><span class="line">print(x <= y) # False</span><br><span class="line">True</span><br><span class="line">True</span><br><span class="line">False</span><br><span class="line">False</span><br></pre></td></tr></table></figure><ul><li><code>set.issuperset(set)</code>用于判断集合是不是包含其他集合，如果是则返回 True，否则返回 False。</li><li><code>set1 >= set2</code> 判断集合是不是包含其他集合，如果是则返回 True，否则返回 False。</li></ul><p>【例子】</p><p>[72]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">x = {"f", "e", "d", "c", "b", "a"}</span><br><span class="line">y = {"a", "b", "c"}</span><br><span class="line">z = x.issuperset(y)</span><br><span class="line">print(z) # True</span><br><span class="line">print(x >= y) # True</span><br><span class="line"></span><br><span class="line">x = {"f", "e", "d", "c", "b"}</span><br><span class="line">y = {"a", "b", "c"}</span><br><span class="line">z = x.issuperset(y)</span><br><span class="line">print(z) # False</span><br><span class="line">print(x >= y) # False</span><br><span class="line">True</span><br><span class="line">True</span><br><span class="line">False</span><br><span class="line">False</span><br></pre></td></tr></table></figure><ul><li><code>set.isdisjoint(set)</code> 用于判断两个集合是不是不相交，如果是返回 True，否则返回 False。</li></ul><p>【例子】</p><p>[73]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">x = {"f", "e", "d", "c", "b"}</span><br><span class="line">y = {"a", "b", "c"}</span><br><span class="line">z = x.isdisjoint(y)</span><br><span class="line">print(z) # False</span><br><span class="line"></span><br><span class="line">x = {"f", "e", "d", "m", "g"}</span><br><span class="line">y = {"a", "b", "c"}</span><br><span class="line">z = x.isdisjoint(y)</span><br><span class="line">print(z) # True</span><br><span class="line">False</span><br><span class="line">True</span><br></pre></td></tr></table></figure><h2 id="4-集合的转换"><a href="#4-集合的转换" class="headerlink" title="4. 集合的转换"></a>4. 集合的转换</h2><p>【例子】</p><p>[74]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">se = set(range(4))</span><br><span class="line">li = list(se)</span><br><span class="line">tu = tuple(se)</span><br><span class="line"></span><br><span class="line">print(se, type(se)) # {0, 1, 2, 3} <class 'set'></span><br><span class="line">print(li, type(li)) # [0, 1, 2, 3] <class 'list'></span><br><span class="line">print(tu, type(tu)) # (0, 1, 2, 3) <class 'tuple'></span><br><span class="line">{0, 1, 2, 3} <class 'set'></span><br><span class="line">[0, 1, 2, 3] <class 'list'></span><br><span class="line">(0, 1, 2, 3) <class 'tuple'></span><br></pre></td></tr></table></figure><h2 id="5-不可变集合"><a href="#5-不可变集合" class="headerlink" title="5. 不可变集合"></a>5. 不可变集合</h2><p>Python 提供了不能改变元素的集合的实现版本，即不能增加或删除元素，类型名叫<code>frozenset</code>。需要注意的是<code>frozenset</code>仍然可以进行集合操作，只是不能用带有<code>update</code>的方法。</p><ul><li><code>frozenset([iterable])</code> 返回一个冻结的集合，冻结后集合不能再添加或删除任何元素。</li></ul><p>【例子】</p><p>[75]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">a = frozenset(range(10)) # 生成一个新的不可变集合</span><br><span class="line">print(a) </span><br><span class="line"># frozenset({0, 1, 2, 3, 4, 5, 6, 7, 8, 9})</span><br><span class="line"></span><br><span class="line">b = frozenset('lsgogroup')</span><br><span class="line">print(b) </span><br><span class="line"># frozenset({'g', 's', 'p', 'r', 'u', 'o', 'l'})</span><br><span class="line">frozenset({0, 1, 2, 3, 4, 5, 6, 7, 8, 9})</span><br><span class="line">frozenset({'l', 'g', 'r', 'u', 'o', 's', 'p'})</span><br></pre></td></tr></table></figure><h1 id="序列"><a href="#序列" class="headerlink" title="序列"></a>序列</h1><p>在 Python 中，序列类型包括字符串、列表、元组、集合和字典，这些序列支持一些通用的操作，但比较特殊的是，集合和字典不支持索引、切片、相加和相乘操作。</p><h2 id="1-针对序列的内置函数"><a href="#1-针对序列的内置函数" class="headerlink" title="1. 针对序列的内置函数"></a>1. 针对序列的内置函数</h2><ul><li><code>list(sub)</code> 把一个可迭代对象转换为列表。</li></ul><p>【例子】</p><p>[76]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">a = list()</span><br><span class="line">print(a) # []</span><br><span class="line"></span><br><span class="line">b = 'I Love LsgoGroup'</span><br><span class="line">b = list(b)</span><br><span class="line">print(b) </span><br><span class="line"># ['I', ' ', 'L', 'o', 'v', 'e', ' ', 'L', 's', 'g', 'o', 'G', 'r', 'o', 'u', 'p']</span><br><span class="line"></span><br><span class="line">c = (1, 1, 2, 3, 5, 8)</span><br><span class="line">c = list(c)</span><br><span class="line">print(c) # [1, 1, 2, 3, 5, 8]</span><br><span class="line">[]</span><br><span class="line">['I', ' ', 'L', 'o', 'v', 'e', ' ', 'L', 's', 'g', 'o', 'G', 'r', 'o', 'u', 'p']</span><br><span class="line">[1, 1, 2, 3, 5, 8]</span><br></pre></td></tr></table></figure><ul><li><code>tuple(sub)</code> 把一个可迭代对象转换为元组。</li></ul><p>【例子】</p><p>[77]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">a = tuple()</span><br><span class="line">print(a) # ()</span><br><span class="line"></span><br><span class="line">b = 'I Love LsgoGroup'</span><br><span class="line">b = tuple(b)</span><br><span class="line">print(b) </span><br><span class="line"># ('I', ' ', 'L', 'o', 'v', 'e', ' ', 'L', 's', 'g', 'o', 'G', 'r', 'o', 'u', 'p')</span><br><span class="line"></span><br><span class="line">c = [1, 1, 2, 3, 5, 8]</span><br><span class="line">c = tuple(c)</span><br><span class="line">print(c) # (1, 1, 2, 3, 5, 8)</span><br><span class="line">()</span><br><span class="line">('I', ' ', 'L', 'o', 'v', 'e', ' ', 'L', 's', 'g', 'o', 'G', 'r', 'o', 'u', 'p')</span><br><span class="line">(1, 1, 2, 3, 5, 8)</span><br></pre></td></tr></table></figure><ul><li><code>str(obj)</code> 把obj对象转换为字符串</li></ul><p>【例子】</p><p>[78]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">a = 123</span><br><span class="line">a = str(a)</span><br><span class="line">print(a) # 123</span><br><span class="line">123</span><br></pre></td></tr></table></figure><ul><li><pre><code>len(s)<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line"> 返回对象（字符、列表、元组等）长度或元素个数。</span><br><span class="line"></span><br><span class="line"> - `s` -- 对象。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[79]:</span><br></pre></td></tr></table></figure>a = list()print(len(a)) # 0</code></pre></li></ul><p>b = (‘I’, ‘ ‘, ‘L’, ‘o’, ‘v’, ‘e’, ‘ ‘, ‘L’, ‘s’, ‘g’, ‘o’, ‘G’, ‘r’, ‘o’, ‘u’, ‘p’)<br>print(len(b)) # 16</p><p>c = ‘I Love LsgoGroup’<br>print(len(c)) # 16<br>0<br>16<br>16</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">- `max(sub)`返回序列或者参数集合中的最大值</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[80]:</span><br></pre></td></tr></table></figure><p>print(max(1, 2, 3, 4, 5)) # 5<br>print(max([-8, 99, 3, 7, 83])) # 99<br>print(max(‘IloveLsgoGroup’)) # v<br>5<br>99<br>v</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">- `min(sub)`返回序列或参数集合中的最小值</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[81]:</span><br></pre></td></tr></table></figure><p>print(min(1, 2, 3, 4, 5)) # 1<br>print(min([-8, 99, 3, 7, 83])) # -8<br>print(min(‘IloveLsgoGroup’)) # G<br>1<br>-8<br>G</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">- `sum(iterable[, start=0])` 返回序列`iterable`与可选参数`start`的总和。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[82]:</span><br></pre></td></tr></table></figure><p>print(sum([1, 3, 5, 7, 9])) # 25<br>print(sum([1, 3, 5, 7, 9], 10)) # 35<br>print(sum((1, 3, 5, 7, 9))) # 25<br>print(sum((1, 3, 5, 7, 9), 20)) # 45<br>25<br>35<br>25<br>45</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">-</span><br></pre></td></tr></table></figure><p> sorted(iterable, key=None, reverse=False)<br> <figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line"> 对所有可迭代的对象进行排序操作。</span><br><span class="line"></span><br><span class="line"> - `iterable` -- 可迭代对象。</span><br><span class="line"> - `key` -- 主要是用来进行比较的元素，只有一个参数，具体的函数的参数就是取自于可迭代对象中，指定可迭代对象中的一个元素来进行排序。</span><br><span class="line"> - `reverse` -- 排序规则，`reverse = True` 降序 ， `reverse = False` 升序（默认）。</span><br><span class="line"> - 返回重新排序的列表。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[83]:</span><br></pre></td></tr></table></figure><br>x = [-8, 99, 3, 7, 83]<br>print(sorted(x)) # [-8, 3, 7, 83, 99]<br>print(sorted(x, reverse=True)) # [99, 83, 7, 3, -8]</p><p>t = ({“age”: 20, “name”: “a”}, {“age”: 25, “name”: “b”}, {“age”: 10, “name”: “c”})<br>x = sorted(t, key=lambda a: a[“age”])<br>print(x)</p><h1 id="‘age’-10-‘name’-‘c’-‘age’-20-‘name’-‘a’-‘age’-25-‘name’-‘b’"><a href="#‘age’-10-‘name’-‘c’-‘age’-20-‘name’-‘a’-‘age’-25-‘name’-‘b’" class="headerlink" title="[{‘age’: 10, ‘name’: ‘c’}, {‘age’: 20, ‘name’: ‘a’}, {‘age’: 25, ‘name’: ‘b’}]"></a>[{‘age’: 10, ‘name’: ‘c’}, {‘age’: 20, ‘name’: ‘a’}, {‘age’: 25, ‘name’: ‘b’}]</h1><p>[-8, 3, 7, 83, 99]<br>[99, 83, 7, 3, -8]<br>[{‘age’: 10, ‘name’: ‘c’}, {‘age’: 20, ‘name’: ‘a’}, {‘age’: 25, ‘name’: ‘b’}]</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">-</span><br></pre></td></tr></table></figure><p> reversed(seq)<br> <figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"> </span><br><span class="line"></span><br><span class="line"> 函数返回一个反转的迭代器。</span><br><span class="line"></span><br><span class="line"> - `seq` -- 要转换的序列，可以是 tuple, string, list 或 range。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[84]:</span><br></pre></td></tr></table></figure><br>s = ‘lsgogroup’<br>x = reversed(s)<br>print(type(x)) # <class ‘reversed’><br>print(x) # <reversed object at 0x000002507E8EC2C8><br>print(list(x))</p><h1 id="‘p’-‘u’-‘o’-‘r’-‘g’-‘o’-‘g’-‘s’-‘l’"><a href="#‘p’-‘u’-‘o’-‘r’-‘g’-‘o’-‘g’-‘s’-‘l’" class="headerlink" title="[‘p’, ‘u’, ‘o’, ‘r’, ‘g’, ‘o’, ‘g’, ‘s’, ‘l’]"></a>[‘p’, ‘u’, ‘o’, ‘r’, ‘g’, ‘o’, ‘g’, ‘s’, ‘l’]</h1><p>t = (‘l’, ‘s’, ‘g’, ‘o’, ‘g’, ‘r’, ‘o’, ‘u’, ‘p’)<br>print(list(reversed(t)))</p><h1 id="‘p’-‘u’-‘o’-‘r’-‘g’-‘o’-‘g’-‘s’-‘l’-1"><a href="#‘p’-‘u’-‘o’-‘r’-‘g’-‘o’-‘g’-‘s’-‘l’-1" class="headerlink" title="[‘p’, ‘u’, ‘o’, ‘r’, ‘g’, ‘o’, ‘g’, ‘s’, ‘l’]"></a>[‘p’, ‘u’, ‘o’, ‘r’, ‘g’, ‘o’, ‘g’, ‘s’, ‘l’]</h1><p>r = range(5, 9)<br>print(list(reversed(r)))</p><h1 id="8-7-6-5"><a href="#8-7-6-5" class="headerlink" title="[8, 7, 6, 5]"></a>[8, 7, 6, 5]</h1><p>x = [-8, 99, 3, 7, 83]<br>print(list(reversed(x)))</p><h1 id="83-7-3-99-8"><a href="#83-7-3-99-8" class="headerlink" title="[83, 7, 3, 99, -8]"></a>[83, 7, 3, 99, -8]</h1><p><class ‘reversed’><br><reversed object at 0x000001F0517DFD68><br>[‘p’, ‘u’, ‘o’, ‘r’, ‘g’, ‘o’, ‘g’, ‘s’, ‘l’]<br>[‘p’, ‘u’, ‘o’, ‘r’, ‘g’, ‘o’, ‘g’, ‘s’, ‘l’]<br>[8, 7, 6, 5]<br>[83, 7, 3, 99, -8]</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">- `enumerate(sequence, [start=0])`</span><br><span class="line"></span><br><span class="line">【例子】用于将一个可遍历的数据对象(如列表、元组或字符串)组合为一个索引序列，同时列出数据和数据下标，一般用在 for 循环当中。</span><br><span class="line"></span><br><span class="line">[85]:</span><br></pre></td></tr></table></figure><p>seasons = [‘Spring’, ‘Summer’, ‘Fall’, ‘Winter’]<br>a = list(enumerate(seasons))<br>print(a) </p><h1 id="0-‘Spring’-1-‘Summer’-2-‘Fall’-3-‘Winter’"><a href="#0-‘Spring’-1-‘Summer’-2-‘Fall’-3-‘Winter’" class="headerlink" title="[(0, ‘Spring’), (1, ‘Summer’), (2, ‘Fall’), (3, ‘Winter’)]"></a>[(0, ‘Spring’), (1, ‘Summer’), (2, ‘Fall’), (3, ‘Winter’)]</h1><p>b = list(enumerate(seasons, 1))<br>print(b) </p><h1 id="1-‘Spring’-2-‘Summer’-3-‘Fall’-4-‘Winter’"><a href="#1-‘Spring’-2-‘Summer’-3-‘Fall’-4-‘Winter’" class="headerlink" title="[(1, ‘Spring’), (2, ‘Summer’), (3, ‘Fall’), (4, ‘Winter’)]"></a>[(1, ‘Spring’), (2, ‘Summer’), (3, ‘Fall’), (4, ‘Winter’)]</h1><p>for i, element in a:<br> print(‘{0},{1}’.format(i, element))</p><h1 id="0-Spring"><a href="#0-Spring" class="headerlink" title="0,Spring"></a>0,Spring</h1><h1 id="1-Summer"><a href="#1-Summer" class="headerlink" title="1,Summer"></a>1,Summer</h1><h1 id="2-Fall"><a href="#2-Fall" class="headerlink" title="2,Fall"></a>2,Fall</h1><h1 id="3-Winter"><a href="#3-Winter" class="headerlink" title="3,Winter"></a>3,Winter</h1><p>[(0, ‘Spring’), (1, ‘Summer’), (2, ‘Fall’), (3, ‘Winter’)]<br>[(1, ‘Spring’), (2, ‘Summer’), (3, ‘Fall’), (4, ‘Winter’)]<br>0,Spring<br>1,Summer<br>2,Fall<br>3,Winter</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line">-</span><br></pre></td></tr></table></figure><p> zip(iter1 [,iter2 […]])<br> <figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"></span><br><span class="line"> - 用于将可迭代的对象作为参数，将对象中对应的元素打包成一个个元组，然后返回由这些元组组成的对象，这样做的好处是节约了不少的内存。</span><br><span class="line"> - 我们可以使用 `list()` 转换来输出列表。</span><br><span class="line"> - 如果各个迭代器的元素个数不一致，则返回列表长度与最短的对象相同，利用 `*` 号操作符，可以将元组解压为列表。</span><br><span class="line"></span><br><span class="line">【例子】</span><br><span class="line"></span><br><span class="line">[86]:</span><br></pre></td></tr></table></figure><br>a = [1, 2, 3]<br>b = [4, 5, 6]<br>c = [4, 5, 6, 7, 8]</p><p>zipped = zip(a, b)<br>print(zipped) # <zip object at 0x000000C5D89EDD88><br>print(list(zipped)) # [(1, 4), (2, 5), (3, 6)]<br>zipped = zip(a, c)<br>print(list(zipped)) # [(1, 4), (2, 5), (3, 6)]</p><p>a1, a2 = zip(*zip(a, b))<br>print(list(a1)) # [1, 2, 3]<br>print(list(a2)) # [4, 5, 6]<br><zip object at 0x000001F0517E38C8><br>[(1, 4), (2, 5), (3, 6)]<br>[(1, 4), (2, 5), (3, 6)]<br>[1, 2, 3]<br>[4, 5, 6]<br>```</p>]]></content>
<summary type="html"><h1 id="Python入门-中"><a href="#Python入门-中" class="headerlink" title="Python入门(中)"></a>Python入门(中)</h1><p>[TOC]</p>
<h1 id="简介"><a href="#简介" </summary>
<category term="python基础" scheme="https://wicherqaq.github.io/categories/python%E5%9F%BA%E7%A1%80/"/>
</entry>
<entry>
<title>python入门（上）</title>
<link href="https://wicherqaq.github.io/2020/09/10/python%E5%85%A5%E9%97%A8%EF%BC%88%E4%B8%8A%EF%BC%89/"/>
<id>https://wicherqaq.github.io/2020/09/10/python%E5%85%A5%E9%97%A8%EF%BC%88%E4%B8%8A%EF%BC%89/</id>
<published>2020-09-10T02:51:11.000Z</published>
<updated>2020-09-10T02:57:24.512Z</updated>
<content type="html"><![CDATA[<h1 id="Python入门-上"><a href="#Python入门-上" class="headerlink" title="Python入门(上)"></a>Python入门(上)</h1><p>[TOC]</p><h1 id="简介"><a href="#简介" class="headerlink" title="简介"></a>简介</h1><p>Python 是一种通用编程语言，其在科学计算和机器学习领域具有广泛的应用。如果我们打算利用 Python 来执行机器学习，那么对 Python 有一些基本的了解就是至关重要的。本 Python 入门系列体验就是为这样的初学者精心准备的。</p><p>本实验包括以下内容：</p><ul><li>变量、运算符与数据类型<ul><li>注释</li><li>运算符</li><li>变量和赋值</li><li>数据类型与转换</li><li>print() 函数</li></ul></li><li>位运算<ul><li>原码、反码和补码</li><li>按位非操作 ~</li><li>按位与操作 &</li><li>按位或操作 |</li><li>按位异或操作 ^</li><li>按位左移操作 <<</li><li>按位右移操作 >></li><li>利用位运算实现快速计算</li><li>利用位运算实现整数集合</li></ul></li><li>条件语句<ul><li>if 语句</li><li>if - else 语句</li><li>if - elif - else 语句</li><li>assert 关键词</li></ul></li><li>循环语句<ul><li>while 循环</li><li>while - else 循环</li><li>for 循环</li><li>for - else 循环</li><li>range() 函数</li><li>enumerate()函数</li><li>break 语句</li><li>continue 语句</li><li>pass 语句</li><li>推导式</li></ul></li><li>异常处理<ul><li>Python 标准异常总结</li><li>Python 标准警告总结</li><li>try - except 语句</li><li>try - except - finally 语句</li><li>try - except - else 语句</li><li>raise语句</li></ul></li></ul><h1 id="变量、运算符与数据类型"><a href="#变量、运算符与数据类型" class="headerlink" title="变量、运算符与数据类型"></a>变量、运算符与数据类型</h1><h2 id="1-注释"><a href="#1-注释" class="headerlink" title="1. 注释"></a>1. 注释</h2><ul><li>在 Python 中，<code>#</code> 表示注释，作用于整行。</li></ul><p>【例子】单行注释</p><p>[1]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"># 这是一个注释</span><br><span class="line">print("Hello world")</span><br><span class="line"></span><br><span class="line"># Hello world</span><br><span class="line">Hello world</span><br></pre></td></tr></table></figure><ul><li><code>''' '''</code> 或者 <code>""" """</code> 表示区间注释，在三引号之间的所有内容被注释</li></ul><p>【例子】多行注释</p><p>[2]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">'''</span><br><span class="line">这是多行注释，用三个单引号</span><br><span class="line">这是多行注释，用三个单引号</span><br><span class="line">这是多行注释，用三个单引号</span><br><span class="line">'''</span><br><span class="line">print("Hello china") </span><br><span class="line"># Hello china</span><br><span class="line"></span><br><span class="line">"""</span><br><span class="line">这是多行注释，用三个双引号</span><br><span class="line">这是多行注释，用三个双引号 </span><br><span class="line">这是多行注释，用三个双引号</span><br><span class="line">"""</span><br><span class="line">print("hello china") </span><br><span class="line"># hello china</span><br><span class="line">Hello china</span><br><span class="line">hello china</span><br></pre></td></tr></table></figure><h2 id="2-运算符"><a href="#2-运算符" class="headerlink" title="2. 运算符"></a>2. 运算符</h2><p><strong>算术运算符</strong></p><table><thead><tr><th>操作符</th><th>名称</th><th>示例</th></tr></thead><tbody><tr><td><code>+</code></td><td>加</td><td><code>1 + 1</code></td></tr><tr><td><code>-</code></td><td>减</td><td><code>2 - 1</code></td></tr><tr><td><code>*</code></td><td>乘</td><td><code>3 * 4</code></td></tr><tr><td><code>/</code></td><td>除</td><td><code>3 / 4</code></td></tr><tr><td><code>//</code></td><td>整除（地板除）</td><td><code>3 // 4</code></td></tr><tr><td><code>%</code></td><td>取余</td><td><code>3 % 4</code></td></tr><tr><td><code>**</code></td><td>幂</td><td><code>2 ** 3</code></td></tr></tbody></table><p>【例子】</p><p>[4]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line">print(1 + 1) # 2</span><br><span class="line">print(2 - 1) # 1</span><br><span class="line">print(3 * 4) # 12</span><br><span class="line">print(3 / 4) # 0.75</span><br><span class="line">print(3 // 4) # 0</span><br><span class="line">print(3 % 4) # 3</span><br><span class="line">print(2 ** 4) # 8</span><br><span class="line">print(5//10)</span><br><span class="line">2</span><br><span class="line">1</span><br><span class="line">12</span><br><span class="line">0.75</span><br><span class="line">0</span><br><span class="line">3</span><br><span class="line">16</span><br><span class="line">0</span><br></pre></td></tr></table></figure><p><strong>比较运算符</strong></p><table><thead><tr><th>操作符</th><th>名称</th><th>示例</th></tr></thead><tbody><tr><td><code>></code></td><td>大于</td><td><code>2 > 1</code></td></tr><tr><td><code>>=</code></td><td>大于等于</td><td><code>2 >= 4</code></td></tr><tr><td><code><</code></td><td>小于</td><td><code>1 < 2</code></td></tr><tr><td><code><=</code></td><td>小于等于</td><td><code>5 <= 2</code></td></tr><tr><td><code>==</code></td><td>等于</td><td><code>3 == 4</code></td></tr><tr><td><code>!=</code></td><td>不等于</td><td><code>3 != 5</code></td></tr></tbody></table><p>【例子】</p><p>[4]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">print(2 > 1) # True</span><br><span class="line">print(2 >= 4) # False</span><br><span class="line">print(1 < 2) # True</span><br><span class="line">print(5 <= 2) # False</span><br><span class="line">print(3 == 4) # False</span><br><span class="line">print(3 != 5) # True</span><br><span class="line">True</span><br><span class="line">False</span><br><span class="line">True</span><br><span class="line">False</span><br><span class="line">False</span><br><span class="line">True</span><br></pre></td></tr></table></figure><p><strong>逻辑运算符</strong></p><table><thead><tr><th>操作符</th><th>名称</th><th>示例</th></tr></thead><tbody><tr><td><code>and</code></td><td>与</td><td><code>(3 > 2) and (3 < 5)</code></td></tr><tr><td><code>or</code></td><td>或</td><td><code>(1 > 3) or (9 < 2)</code></td></tr><tr><td><code>not</code></td><td>非</td><td><code>not (2 > 1)</code></td></tr></tbody></table><p>【例子】</p><p>[5]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">print((3 > 2) and (3 < 5)) # True</span><br><span class="line">print((1 > 3) or (9 < 2)) # False</span><br><span class="line">print(not (2 > 1)) # False</span><br><span class="line">True</span><br><span class="line">False</span><br><span class="line">False</span><br></pre></td></tr></table></figure><p><strong>位运算符</strong></p><table><thead><tr><th>操作符</th><th>名称</th><th>示例</th></tr></thead><tbody><tr><td><code>~</code></td><td>按位取反</td><td><code>~4</code></td></tr><tr><td><code>&</code></td><td>按位与</td><td><code>4 & 5</code></td></tr><tr><td>`</td><td>`</td><td>按位或</td></tr><tr><td><code>^</code></td><td>按位异或</td><td><code>4 ^ 5</code></td></tr><tr><td><code><<</code></td><td>左移</td><td><code>4 << 2</code></td></tr><tr><td><code>>></code></td><td>右移</td><td><code>4 >> 2</code></td></tr></tbody></table><p>【例子】有关二进制的运算，参见“位运算”部分的讲解。</p><p>[6]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line">print(bin(4)) # 0b100</span><br><span class="line">print(bin(5)) # 0b101</span><br><span class="line">print(bin(~4), ~4) # -0b101 -5</span><br><span class="line">print(bin(4 & 5), 4 & 5) # 0b100 4</span><br><span class="line">print(bin(4 | 5), 4 | 5) # 0b101 5</span><br><span class="line">print(bin(4 ^ 5), 4 ^ 5) # 0b1 1</span><br><span class="line">print(bin(4 << 2), 4 << 2) # 0b10000 16</span><br><span class="line">print(bin(4 >> 2), 4 >> 2) # 0b1 1</span><br><span class="line">0b100</span><br><span class="line">0b101</span><br><span class="line">-0b101 -5</span><br><span class="line">0b100 4</span><br><span class="line">0b101 5</span><br><span class="line">0b1 1</span><br><span class="line">0b10000 16</span><br><span class="line">0b1 1</span><br></pre></td></tr></table></figure><p><strong>三元运算符</strong></p><p>【例子】</p><p>[7]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">x, y = 4, 5</span><br><span class="line">if x < y:</span><br><span class="line"> small = x</span><br><span class="line">else:</span><br><span class="line"> small = y</span><br><span class="line"></span><br><span class="line">print(small) # 4</span><br><span class="line">4</span><br></pre></td></tr></table></figure><p>有了这个三元操作符的条件表达式，你可以使用一条语句来完成以上的条件判断和赋值操作。</p><p>【例子】</p><p>[8]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">x, y = 4, 5</span><br><span class="line">small = x if x < y else y</span><br><span class="line">print(small) # 4</span><br><span class="line">4</span><br></pre></td></tr></table></figure><p><strong>其他运算符</strong></p><table><thead><tr><th>操作符</th><th>名称</th><th>示例</th></tr></thead><tbody><tr><td><code>in</code></td><td>存在</td><td><code>'A' in ['A', 'B', 'C']</code></td></tr><tr><td><code>not in</code></td><td>不存在</td><td><code>'h' not in ['A', 'B', 'C']</code></td></tr><tr><td><code>is</code></td><td>是</td><td><code>"hello" is "hello"</code></td></tr><tr><td><code>not is</code></td><td>不是</td><td><code>"hello" is not "hello"</code></td></tr></tbody></table><p>【例子】</p><p>[9]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">letters = ['A', 'B', 'C']</span><br><span class="line">if 'A' in letters:</span><br><span class="line"> print('A' + ' exists')</span><br><span class="line">if 'h' not in letters:</span><br><span class="line"> print('h' + ' not exists')</span><br><span class="line"></span><br><span class="line"># A exists</span><br><span class="line"># h not exists</span><br><span class="line">A exists</span><br><span class="line">h not exists</span><br></pre></td></tr></table></figure><p>【例子】比较的两个变量均指向不可变类型。</p><p>[10]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">a = "hello"</span><br><span class="line">b = "hello"</span><br><span class="line">print(a is b, a == b) # True True</span><br><span class="line">print(a is not b, a != b) # False False</span><br><span class="line">True True</span><br><span class="line">False False</span><br></pre></td></tr></table></figure><p>【例子】比较的两个变量均指向可变类型。</p><p>[11]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">a = ["hello"]</span><br><span class="line">b = ["hello"]</span><br><span class="line">print(a is b, a == b) # False True</span><br><span class="line">print(a is not b, a != b) # True False</span><br><span class="line">False True</span><br><span class="line">True False</span><br></pre></td></tr></table></figure><p>注意：</p><ul><li>is, is not 对比的是两个变量的内存地址</li><li>==, != 对比的是两个变量的值</li><li>比较的两个变量，指向的都是地址不可变的类型（str等），那么is，is not 和 ==，！= 是完全等价的。</li><li>对比的两个变量，指向的是地址可变的类型（list，dict，tuple等），则两者是有区别的。</li></ul><p><strong>运算符的优先级</strong></p><ul><li>一元运算符优于二元运算符。例如<code>3 ** -2</code>等价于<code>3 ** (-2)</code>。</li><li>先算术运算，后移位运算，最后位运算。例如 <code>1 << 3 + 2 & 7</code>等价于 <code>1 << (3 + 2)) & 7</code>。</li><li>逻辑运算最后结合。例如<code>3 < 4 and 4 < 5</code>等价于<code>(3 < 4) and (4 < 5)</code>。</li></ul><p>【例子】</p><p>[12]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">print(-3 ** 2) # -9</span><br><span class="line">print(3 ** -2) # 0.1111111111111111</span><br><span class="line">print(1 << 3 + 2 & 7) # 0</span><br><span class="line">print(-3 * 2 + 5 / -2 - 4) # -12.5</span><br><span class="line">print(3 < 4 and 4 < 5) # True</span><br><span class="line">-9</span><br><span class="line">0.1111111111111111</span><br><span class="line">0</span><br><span class="line">-12.5</span><br><span class="line">True</span><br></pre></td></tr></table></figure><h2 id="3-变量和赋值"><a href="#3-变量和赋值" class="headerlink" title="3. 变量和赋值"></a>3. 变量和赋值</h2><ul><li>在使用变量之前，需要对其先赋值。</li><li>变量名可以包括字母、数字、下划线、但变量名不能以数字开头。</li><li>Python 变量名是大小写敏感的，foo != Foo。</li></ul><p>【例子】</p><p>[13]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">teacher = "老马的程序人生"</span><br><span class="line">print(teacher) # 老马的程序人生</span><br><span class="line">老马的程序人生</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[14]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">first = 2</span><br><span class="line">second = 3</span><br><span class="line">third = first + second</span><br><span class="line">print(third) # 5</span><br><span class="line">5</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[15]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">myTeacher = "老马的程序人生"</span><br><span class="line">yourTeacher = "小马的程序人生"</span><br><span class="line">ourTeacher = myTeacher + ',' + yourTeacher</span><br><span class="line">print(ourTeacher) # 老马的程序人生,小马的程序人生</span><br><span class="line">老马的程序人生,小马的程序人生</span><br></pre></td></tr></table></figure><h2 id="4-数据类型与转换"><a href="#4-数据类型与转换" class="headerlink" title="4. 数据类型与转换"></a>4. 数据类型与转换</h2><table><thead><tr><th>类型</th><th>名称</th><th>示例</th></tr></thead><tbody><tr><td>int</td><td>整型 <code><class 'int'></code></td><td><code>-876, 10</code></td></tr><tr><td>float</td><td>浮点型<code><class 'float'></code></td><td><code>3.149, 11.11</code></td></tr><tr><td>bool</td><td>布尔型<code><class 'bool'></code></td><td><code>True, False</code></td></tr></tbody></table><p><strong>整型</strong></p><p>【例子】通过 <code>print()</code> 可看出 <code>a</code> 的值，以及类 (class) 是<code>int</code>。</p><p>[16]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">a = 1031</span><br><span class="line">print(a, type(a))</span><br><span class="line"># 1031 <class 'int'></span><br><span class="line">1031 <class 'int'></span><br></pre></td></tr></table></figure><p>Python 里面万物皆对象（object），整型也不例外，只要是对象，就有相应的属性 （attributes） 和方法（methods）。</p><p>【例子】</p><p>[17]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">b = dir(int)</span><br><span class="line">print(b)</span><br><span class="line"></span><br><span class="line"># ['__abs__', '__add__', '__and__', '__bool__', '__ceil__', '__class__',</span><br><span class="line"># '__delattr__', '__dir__', '__divmod__', '__doc__', '__eq__',</span><br><span class="line"># '__float__', '__floor__', '__floordiv__', '__format__', '__ge__',</span><br><span class="line"># '__getattribute__', '__getnewargs__', '__gt__', '__hash__',</span><br><span class="line"># '__index__', '__init__', '__init_subclass__', '__int__', '__invert__',</span><br><span class="line"># '__le__', '__lshift__', '__lt__', '__mod__', '__mul__', '__ne__',</span><br><span class="line"># '__neg__', '__new__', '__or__', '__pos__', '__pow__', '__radd__',</span><br><span class="line"># '__rand__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__',</span><br><span class="line"># '__rfloordiv__', '__rlshift__', '__rmod__', '__rmul__', '__ror__',</span><br><span class="line"># '__round__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__',</span><br><span class="line"># '__rtruediv__', '__rxor__', '__setattr__', '__sizeof__', '__str__',</span><br><span class="line"># '__sub__', '__subclasshook__', '__truediv__', '__trunc__', '__xor__',</span><br><span class="line"># 'bit_length', 'conjugate', 'denominator', 'from_bytes', 'imag',</span><br><span class="line"># 'numerator', 'real', 'to_bytes']</span><br><span class="line">['__abs__', '__add__', '__and__', '__bool__', '__ceil__', '__class__', '__delattr__', '__dir__', '__divmod__', '__doc__', '__eq__', '__float__', '__floor__', '__floordiv__', '__format__', '__ge__', '__getattribute__', '__getnewargs__', '__gt__', '__hash__', '__index__', '__init__', '__init_subclass__', '__int__', '__invert__', '__le__', '__lshift__', '__lt__', '__mod__', '__mul__', '__ne__', '__neg__', '__new__', '__or__', '__pos__', '__pow__', '__radd__', '__rand__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rlshift__', '__rmod__', '__rmul__', '__ror__', '__round__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', '__trunc__', '__xor__', 'bit_length', 'conjugate', 'denominator', 'from_bytes', 'imag', 'numerator', 'real', 'to_bytes']</span><br></pre></td></tr></table></figure><p>对它们有个大概印象就可以了，具体怎么用，需要哪些参数 （argument），还需要查文档。看个<code>bit_length()</code>的例子。</p><p>【例子】找到一个整数的二进制表示，再返回其长度。</p><p>[18]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">a = 1031</span><br><span class="line">print(bin(a)) # 0b10000000111</span><br><span class="line">print(a.bit_length()) # 11</span><br><span class="line">0b10000000111</span><br><span class="line">11</span><br></pre></td></tr></table></figure><p><strong>浮点型</strong></p><p>【例子】</p><p>[19]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">print(1, type(1))</span><br><span class="line"># 1 <class 'int'></span><br><span class="line"></span><br><span class="line">print(1., type(1.))</span><br><span class="line"># 1.0 <class 'float'></span><br><span class="line"></span><br><span class="line">a = 0.00000023</span><br><span class="line">b = 2.3e-7</span><br><span class="line">print(a) # 2.3e-07</span><br><span class="line">print(b) # 2.3e-07</span><br><span class="line">1 <class 'int'></span><br><span class="line">1.0 <class 'float'></span><br><span class="line">2.3e-07</span><br><span class="line">2.3e-07</span><br></pre></td></tr></table></figure><p>有时候我们想保留浮点型的小数点后 <code>n</code> 位。可以用 <code>decimal</code> 包里的 <code>Decimal</code> 对象和 <code>getcontext()</code> 方法来实现。</p><p>[21]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">import decimal</span><br><span class="line">from decimal import Decimal</span><br></pre></td></tr></table></figure><p>Python 里面有很多用途广泛的包 (package)，用什么你就引进 (import) 什么。包也是对象，也可以用上面提到的<code>dir(decimal)</code> 来看其属性和方法。</p><p>【例子】<code>getcontext()</code> 显示了 <code>Decimal</code> 对象的默认精度值是 28 位 (<code>prec=28</code>)。</p><p>[22]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">a = decimal.getcontext()</span><br><span class="line">print(a)</span><br><span class="line"></span><br><span class="line"># Context(prec=28, rounding=ROUND_HALF_EVEN, Emin=-999999, Emax=999999,</span><br><span class="line"># capitals=1, clamp=0, flags=[], </span><br><span class="line"># traps=[InvalidOperation, DivisionByZero, Overflow])</span><br><span class="line">Context(prec=28, rounding=ROUND_HALF_EVEN, Emin=-999999, Emax=999999, capitals=1, clamp=0, flags=[], traps=[InvalidOperation, DivisionByZero, Overflow])</span><br></pre></td></tr></table></figure><p>[23]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">b = Decimal(1) / Decimal(3)</span><br><span class="line">print(b)</span><br><span class="line"></span><br><span class="line"># 0.3333333333333333333333333333</span><br><span class="line">0.3333333333333333333333333333</span><br></pre></td></tr></table></figure><p>【例子】使 1/3 保留 4 位，用 <code>getcontext().prec</code> 来调整精度。</p><p>[24]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">decimal.getcontext().prec = 4</span><br><span class="line">c = Decimal(1) / Decimal(3)</span><br><span class="line">print(c)</span><br><span class="line"></span><br><span class="line"># 0.3333</span><br><span class="line">0.3333</span><br></pre></td></tr></table></figure><p><strong>布尔型</strong></p><p>布尔 (boolean) 型变量只能取两个值，<code>True</code> 和 <code>False</code>。当把布尔型变量用在数字运算中，用 <code>1</code> 和 <code>0</code> 代表 <code>True</code> 和 <code>False</code>。</p><p>【例子】</p><p>[25]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">print(True + True) # 2</span><br><span class="line">print(True + False) # 1</span><br><span class="line">print(True * False) # 0</span><br><span class="line">2</span><br><span class="line">1</span><br><span class="line">0</span><br></pre></td></tr></table></figure><p>除了直接给变量赋值 <code>True</code> 和 <code>False</code>，还可以用 <code>bool(X)</code> 来创建变量，其中 <code>X</code> 可以是</p><ul><li>基本类型：整型、浮点型、布尔型</li><li>容器类型：字符串、元组、列表、字典和集合</li></ul><p>【例子】<code>bool</code> 作用在基本类型变量：<code>X</code> 只要不是整型 <code>0</code>、浮点型 <code>0.0</code>，<code>bool(X)</code> 就是 <code>True</code>，其余就是 <code>False</code>。</p><p>[26]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">print(type(0), bool(0), bool(1))</span><br><span class="line"># <class 'int'> False True</span><br><span class="line"></span><br><span class="line">print(type(10.31), bool(0.00), bool(10.31))</span><br><span class="line"># <class 'float'> False True</span><br><span class="line"></span><br><span class="line">print(type(True), bool(False), bool(True))</span><br><span class="line"># <class 'bool'> False True</span><br><span class="line"><class 'int'> False True</span><br><span class="line"><class 'float'> False True</span><br><span class="line"><class 'bool'> False True</span><br></pre></td></tr></table></figure><p>【例子】<code>bool</code> 作用在容器类型变量：<code>X</code> 只要不是空的变量，<code>bool(X)</code> 就是 <code>True</code>，其余就是 <code>False</code>。</p><p>[27]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line">print(type(''), bool(''), bool('python'))</span><br><span class="line"># <class 'str'> False True</span><br><span class="line"></span><br><span class="line">print(type(()), bool(()), bool((10,)))</span><br><span class="line"># <class 'tuple'> False True</span><br><span class="line"></span><br><span class="line">print(type([]), bool([]), bool([1, 2]))</span><br><span class="line"># <class 'list'> False True</span><br><span class="line"></span><br><span class="line">print(type({}), bool({}), bool({'a': 1, 'b': 2}))</span><br><span class="line"># <class 'dict'> False True</span><br><span class="line"></span><br><span class="line">print(type(set()), bool(set()), bool({1, 2}))</span><br><span class="line"># <class 'set'> False True</span><br><span class="line"><class 'str'> False True</span><br><span class="line"><class 'tuple'> False True</span><br><span class="line"><class 'list'> False True</span><br><span class="line"><class 'dict'> False True</span><br><span class="line"><class 'set'> False True</span><br></pre></td></tr></table></figure><p>确定<code>bool(X)</code> 的值是 <code>True</code> 还是 <code>False</code>，就看 <code>X</code> 是不是空，空的话就是 <code>False</code>，不空的话就是 <code>True</code>。</p><ul><li>对于数值变量，<code>0</code>, <code>0.0</code> 都可认为是空的。</li><li>对于容器变量，里面没元素就是空的。</li></ul><p><strong>获取类型信息</strong></p><ul><li>获取类型信息 <code>type(object)</code></li></ul><p>【例子】</p><p>[28]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">print(isinstance(1, int)) # True</span><br><span class="line">print(isinstance(5.2, float)) # True</span><br><span class="line">print(isinstance(True, bool)) # True</span><br><span class="line">print(isinstance('5.2', str)) # True</span><br><span class="line">True</span><br><span class="line">True</span><br><span class="line">True</span><br><span class="line">True</span><br></pre></td></tr></table></figure><p>注：</p><ul><li><code>type()</code> 不会认为子类是一种父类类型，不考虑继承关系。</li><li><code>isinstance()</code> 会认为子类是一种父类类型，考虑继承关系。</li></ul><p>如果要判断两个类型是否相同推荐使用 <code>isinstance()</code>。</p><p><strong>类型转换</strong></p><ul><li>转换为整型 <code>int(x, base=10)</code></li><li>转换为字符串 <code>str(object='')</code></li><li>转换为浮点型 <code>float(x)</code></li></ul><p>【例子】</p><p>[29]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">print(int('520')) # 520</span><br><span class="line">print(int(520.52)) # 520</span><br><span class="line">print(float('520.52')) # 520.52</span><br><span class="line">print(float(520)) # 520.0</span><br><span class="line">print(str(10 + 10)) # 20</span><br><span class="line">print(str(10.1 + 5.2)) # 15.3</span><br><span class="line">520</span><br><span class="line">520</span><br><span class="line">520.52</span><br><span class="line">520.0</span><br><span class="line">20</span><br><span class="line">15.3</span><br></pre></td></tr></table></figure><h2 id="5-print-函数"><a href="#5-print-函数" class="headerlink" title="5. print() 函数"></a>5. print() 函数</h2><p>[ ]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)</span><br></pre></td></tr></table></figure><ul><li>将对象以字符串表示的方式格式化输出到流文件对象file里。其中所有非关键字参数都按<code>str()</code>方式进行转换为字符串输出；</li><li>关键字参数<code>sep</code>是实现分隔符，比如多个参数输出时想要输出中间的分隔字符；</li><li>关键字参数<code>end</code>是输出结束时的字符，默认是换行符<code>\n</code>；</li><li>关键字参数<code>file</code>是定义流输出的文件，可以是标准的系统输出<code>sys.stdout</code>，也可以重定义为别的文件；</li><li>关键字参数<code>flush</code>是立即把内容输出到流文件，不作缓存。</li></ul><p>【例子】没有参数时，每次输出后都会换行。</p><p>[31]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">shoplist = ['apple', 'mango', 'carrot', 'banana']</span><br><span class="line">print("This is printed without 'end'and 'sep'.")</span><br><span class="line">for item in shoplist:</span><br><span class="line"> print(item)</span><br><span class="line"></span><br><span class="line"># This is printed without 'end'and 'sep'.</span><br><span class="line"># apple</span><br><span class="line"># mango</span><br><span class="line"># carrot</span><br><span class="line"># banana</span><br><span class="line">This is printed without 'end'and 'sep'.</span><br><span class="line">apple</span><br><span class="line">mango</span><br><span class="line">carrot</span><br><span class="line">banana</span><br></pre></td></tr></table></figure><p>【例子】每次输出结束都用<code>end</code>设置的参数<code>&</code>结尾，并没有默认换行。</p><p>[32]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">shoplist = ['apple', 'mango', 'carrot', 'banana']</span><br><span class="line">print("This is printed with 'end='&''.")</span><br><span class="line">for item in shoplist:</span><br><span class="line"> print(item, end='&')</span><br><span class="line">print('hello world')</span><br><span class="line"></span><br><span class="line"># This is printed with 'end='&''.</span><br><span class="line"># apple&mango&carrot&banana&hello world</span><br><span class="line">This is printed with 'end='&''.</span><br><span class="line">apple&mango&carrot&banana&hello world</span><br></pre></td></tr></table></figure><p>【例子】<code>item</code>值与<code>'another string'</code>两个值之间用<code>sep</code>设置的参数<code>&</code>分割。由于<code>end</code>参数没有设置，因此默认是输出解释后换行，即<code>end</code>参数的默认值为<code>\n</code>。</p><p>[33]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">shoplist = ['apple', 'mango', 'carrot', 'banana']</span><br><span class="line">print("This is printed with 'sep='&''.")</span><br><span class="line">for item in shoplist:</span><br><span class="line"> print(item, 'another string', sep='&')</span><br><span class="line"></span><br><span class="line"># This is printed with 'sep='&''.</span><br><span class="line"># apple&another string</span><br><span class="line"># mango&another string</span><br><span class="line"># carrot&another string</span><br><span class="line"># banana&another string</span><br><span class="line">This is printed with 'sep='&''.</span><br><span class="line">apple&another string</span><br><span class="line">mango&another string</span><br><span class="line">carrot&another string</span><br><span class="line">banana&another string</span><br></pre></td></tr></table></figure><h1 id="位运算"><a href="#位运算" class="headerlink" title="位运算"></a>位运算</h1><h2 id="1-原码、反码和补码"><a href="#1-原码、反码和补码" class="headerlink" title="1. 原码、反码和补码"></a>1. 原码、反码和补码</h2><p>二进制有三种不同的表示形式：原码、反码和补码，计算机内部使用补码来表示。</p><p><strong>原码</strong>：就是其二进制表示（注意，有一位符号位）。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">00 00 00 11 -> 3</span><br><span class="line">10 00 00 11 -> -3</span><br></pre></td></tr></table></figure><p><strong>反码</strong>：正数的反码就是原码，负数的反码是符号位不变，其余位取反（对应正数按位取反）。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">00 00 00 11 -> 3</span><br><span class="line">11 11 11 00 -> -3</span><br></pre></td></tr></table></figure><p><strong>补码</strong>：正数的补码就是原码，负数的补码是反码+1。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">00 00 00 11 -> 3</span><br><span class="line">11 11 11 01 -> -3</span><br></pre></td></tr></table></figure><p><strong>符号位</strong>：最高位为符号位，0表示正数，1表示负数。在位运算中符号位也参与运算。</p><h2 id="2-按位运算"><a href="#2-按位运算" class="headerlink" title="2. 按位运算"></a>2. 按位运算</h2><ul><li>按位非操作 ~</li></ul><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">~ <span class="number">1</span> = <span class="number">0</span></span><br><span class="line">~ <span class="number">0</span> = <span class="number">1</span></span><br></pre></td></tr></table></figure><p><code>~</code> 把<code>num</code>的补码中的 0 和 1 全部取反（0 变为 1，1 变为 0）有符号整数的符号位在 <code>~</code> 运算中同样会取反。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">00 00 01 01 -> 5</span><br><span class="line">~</span><br><span class="line">---</span><br><span class="line">11 11 10 10 -> -6</span><br><span class="line"></span><br><span class="line">11 11 10 11 -> -5</span><br><span class="line">~</span><br><span class="line">---</span><br><span class="line">00 00 01 00 -> 4</span><br></pre></td></tr></table></figure><ul><li>按位与操作 &</li></ul><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1</span> & <span class="number">1</span> = <span class="number">1</span></span><br><span class="line"><span class="number">1</span> & <span class="number">0</span> = <span class="number">0</span></span><br><span class="line"><span class="number">0</span> & <span class="number">1</span> = <span class="number">0</span></span><br><span class="line"><span class="number">0</span> & <span class="number">0</span> = <span class="number">0</span></span><br></pre></td></tr></table></figure><p>只有两个对应位都为 1 时才为 1</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">00 00 01 01 -> 5</span><br><span class="line">&</span><br><span class="line">00 00 01 10 -> 6</span><br><span class="line">---</span><br><span class="line">00 00 01 00 -> 4</span><br></pre></td></tr></table></figure><ul><li>按位或操作 |</li></ul><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1</span> | <span class="number">1</span> = <span class="number">1</span></span><br><span class="line"><span class="number">1</span> | <span class="number">0</span> = <span class="number">1</span></span><br><span class="line"><span class="number">0</span> | <span class="number">1</span> = <span class="number">1</span></span><br><span class="line"><span class="number">0</span> | <span class="number">0</span> = <span class="number">0</span></span><br></pre></td></tr></table></figure><p>只要两个对应位中有一个 1 时就为 1</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">00 00 01 01 -> 5</span><br><span class="line">|</span><br><span class="line">00 00 01 10 -> 6</span><br><span class="line">---</span><br><span class="line">00 00 01 11 -> 7</span><br></pre></td></tr></table></figure><ul><li>按位异或操作 ^</li></ul><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">1</span> ^ <span class="number">1</span> = <span class="number">0</span></span><br><span class="line"><span class="number">1</span> ^ <span class="number">0</span> = <span class="number">1</span></span><br><span class="line"><span class="number">0</span> ^ <span class="number">1</span> = <span class="number">1</span></span><br><span class="line"><span class="number">0</span> ^ <span class="number">0</span> = <span class="number">0</span></span><br></pre></td></tr></table></figure><p>只有两个对应位不同时才为 1</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">00 00 01 01 -> 5</span><br><span class="line">^</span><br><span class="line">00 00 01 10 -> 6</span><br><span class="line">---</span><br><span class="line">00 00 00 11 -> 3</span><br></pre></td></tr></table></figure><p>异或操作的性质：满足交换律和结合律</p><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">A: <span class="number">00</span> <span class="number">00</span> <span class="number">11</span> <span class="number">00</span></span><br><span class="line">B: <span class="number">00</span> <span class="number">00</span> <span class="number">01</span> <span class="number">11</span></span><br><span class="line"></span><br><span class="line">A^B: <span class="number">00</span> <span class="number">00</span> <span class="number">10</span> <span class="number">11</span></span><br><span class="line">B^A: <span class="number">00</span> <span class="number">00</span> <span class="number">10</span> <span class="number">11</span></span><br><span class="line"></span><br><span class="line">A^A: <span class="number">00</span> <span class="number">00</span> <span class="number">00</span> <span class="number">00</span></span><br><span class="line">A^<span class="number">0</span>: <span class="number">00</span> <span class="number">00</span> <span class="number">11</span> <span class="number">00</span></span><br><span class="line"></span><br><span class="line">A^B^A: = A^A^B = B = <span class="number">00</span> <span class="number">00</span> <span class="number">01</span> <span class="number">11</span></span><br></pre></td></tr></table></figure><ul><li>按位左移操作 <<</li></ul><p><code>num << i</code> 将<code>num</code>的二进制表示向左移动<code>i</code>位所得的值。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">00 00 10 11 -> 11</span><br><span class="line"><span class="number">11</span> << <span class="number">3</span></span><br><span class="line">---</span><br><span class="line">01 01 10 00 -> 88</span><br></pre></td></tr></table></figure><ul><li>按位右移操作 >></li></ul><p><code>num >> i</code> 将<code>num</code>的二进制表示向右移动<code>i</code>位所得的值。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">00 00 10 11 -> 11</span><br><span class="line"><span class="number">11</span> >> <span class="number">2</span></span><br><span class="line">---</span><br><span class="line">00 00 00 10 -> 2</span><br></pre></td></tr></table></figure><h2 id="3-利用位运算实现快速计算"><a href="#3-利用位运算实现快速计算" class="headerlink" title="3. 利用位运算实现快速计算"></a>3. 利用位运算实现快速计算</h2><p>通过 <code><<</code>，<code>>></code> 快速计算2的倍数问题。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">n << 1 -> 计算 n*2</span><br><span class="line">n >> 1 -> 计算 n/2，负奇数的运算不可用</span><br><span class="line">n << m -> 计算 n*(2^m)，即乘以 2 的 m 次方</span><br><span class="line">n >> m -> 计算 n/(2^m)，即除以 2 的 m 次方</span><br><span class="line">1 << n -> 2^n</span><br></pre></td></tr></table></figure><p>通过 <code>^</code> 快速交换两个整数。 通过 <code>^</code> 快速交换两个整数。</p><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">a ^= b</span><br><span class="line">b ^= a</span><br><span class="line">a ^= b</span><br></pre></td></tr></table></figure><p>通过 <code>a & (-a)</code> 快速获取<code>a</code>的最后为 1 位置的整数。</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">00 00 01 01 -> 5</span><br><span class="line">&</span><br><span class="line">11 11 10 11 -> -5</span><br><span class="line">---</span><br><span class="line">00 00 00 01 -> 1</span><br><span class="line"></span><br><span class="line">00 00 11 10 -> 14</span><br><span class="line">&</span><br><span class="line">11 11 00 10 -> -14</span><br><span class="line">---</span><br><span class="line">00 00 00 10 -> 2</span><br></pre></td></tr></table></figure><h2 id="4-利用位运算实现整数集合"><a href="#4-利用位运算实现整数集合" class="headerlink" title="4. 利用位运算实现整数集合"></a>4. 利用位运算实现整数集合</h2><p>一个数的二进制表示可以看作是一个集合（0 表示不在集合中，1 表示在集合中）。</p><p>比如集合 <code>{1, 3, 4, 8}</code>，可以表示成 <code>01 00 01 10 10</code> 而对应的位运算也就可以看作是对集合进行的操作。</p><p>元素与集合的操作：</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">a | (1<<i) -> 把 i 插入到集合中</span><br><span class="line">a & ~(1<<i) -> 把 i 从集合中删除</span><br><span class="line">a & (1<<i) -> 判断 i 是否属于该集合（零不属于，非零属于）</span><br></pre></td></tr></table></figure><p>集合之间的操作：</p><figure class="highlight"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">a 补 -> ~a</span><br><span class="line">a 交 b -> a & b</span><br><span class="line">a 并 b -> a | b</span><br><span class="line">a 差 b -> a & (~b)</span><br></pre></td></tr></table></figure><p>注意：整数在内存中是以补码的形式存在的，输出自然也是按照补码输出。</p><p>【例子】C#语言输出负数。</p><p>[ ]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">class Program</span><br><span class="line">{</span><br><span class="line"> static void Main(string[] args)</span><br><span class="line"> {</span><br><span class="line"> string s1 = Convert.ToString(-3, 2);</span><br><span class="line"> Console.WriteLine(s1); </span><br><span class="line"> // 11111111111111111111111111111101</span><br><span class="line"> </span><br><span class="line"> string s2 = Convert.ToString(-3, 16);</span><br><span class="line"> Console.WriteLine(s2); </span><br><span class="line"> // fffffffd</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>【例子】 Python 的<code>bin()</code> 输出。</p><p>[37]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">print(bin(3)) # 0b11</span><br><span class="line">print(bin(-3)) # -0b11</span><br><span class="line"></span><br><span class="line">print(bin(-3 & 0xffffffff)) </span><br><span class="line"># 0b11111111111111111111111111111101</span><br><span class="line"></span><br><span class="line">print(bin(0xfffffffd)) </span><br><span class="line"># 0b11111111111111111111111111111101</span><br><span class="line"></span><br><span class="line">print(0xfffffffd) # 4294967293</span><br><span class="line">0b11</span><br><span class="line">-0b11</span><br><span class="line">0b11111111111111111111111111111101</span><br><span class="line">0b11111111111111111111111111111101</span><br><span class="line">4294967293</span><br></pre></td></tr></table></figure><p>是不是很颠覆认知，我们从结果可以看出：</p><ul><li>Python中<code>bin</code>一个负数（十进制表示），输出的是它的原码的二进制表示加上个负号，巨坑。</li><li>Python中的整型是补码形式存储的。</li><li>Python中整型是不限制长度的不会超范围溢出。</li></ul><p>所以为了获得负数（十进制表示）的补码，需要手动将其和十六进制数<code>0xffffffff</code>进行按位与操作，再交给<code>bin()</code>进行输出，得到的才是负数的补码表示。</p><h1 id="条件语句"><a href="#条件语句" class="headerlink" title="条件语句"></a>条件语句</h1><h2 id="1-if-语句"><a href="#1-if-语句" class="headerlink" title="1. if 语句"></a>1. if 语句</h2><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">if</span> expression:</span><br><span class="line"> expr_true_suite</span><br></pre></td></tr></table></figure><ul><li>if 语句的 <code>expr_true_suite</code> 代码块只有当条件表达式 <code>expression</code> 结果为真时才执行，否则将继续执行紧跟在该代码块后面的语句。</li><li>单个 if 语句中的 <code>expression</code> 条件表达式可以通过布尔操作符 <code>and</code>，<code>or</code>和<code>not</code> 实现多重条件判断。</li></ul><p>【例子】</p><p>[38]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">if 2 > 1 and not 2 > 3:</span><br><span class="line"> print('Correct Judgement!')</span><br><span class="line"></span><br><span class="line"># Correct Judgement!</span><br><span class="line">Correct Judgement!</span><br></pre></td></tr></table></figure><h2 id="2-if-else-语句"><a href="#2-if-else-语句" class="headerlink" title="2. if - else 语句"></a>2. if - else 语句</h2><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">if</span> expression:</span><br><span class="line"> expr_true_suite</span><br><span class="line"><span class="keyword">else</span>:</span><br><span class="line"> expr_false_suite</span><br></pre></td></tr></table></figure><ul><li>Python 提供与 if 搭配使用的 else，如果 if 语句的条件表达式结果布尔值为假，那么程序将执行 else 语句后的代码。</li></ul><p>【例子】</p><p>[39]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">temp = input("猜一猜小姐姐想的是哪个数字？")</span><br><span class="line">guess = int(temp) # input 函数将接收的任何数据类型都默认为 str。</span><br><span class="line">if guess == 666:</span><br><span class="line"> print("你太了解小姐姐的心思了！")</span><br><span class="line"> print("哼，猜对也没有奖励！")</span><br><span class="line">else:</span><br><span class="line"> print("猜错了，小姐姐现在心里想的是666！")</span><br><span class="line">print("游戏结束，不玩儿啦！")</span><br><span class="line">猜一猜小姐姐想的是哪个数字？666</span><br><span class="line">你太了解小姐姐的心思了！</span><br><span class="line">哼，猜对也没有奖励！</span><br><span class="line">游戏结束，不玩儿啦！</span><br></pre></td></tr></table></figure><p><code>if</code>语句支持嵌套，即在一个<code>if</code>语句中嵌入另一个<code>if</code>语句，从而构成不同层次的选择结构。</p><p>【例子】Python 使用缩进而不是大括号来标记代码块边界，因此要特别注意<code>else</code>的悬挂问题。</p><p>[40]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">hi = 6</span><br><span class="line">if hi > 2:</span><br><span class="line"> if hi > 7:</span><br><span class="line"> print('好棒!好棒!')</span><br><span class="line">else:</span><br><span class="line"> print('切~')</span><br><span class="line"></span><br><span class="line"># 无输出</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[41]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">temp = input("猜一猜小姐姐想的是哪个数字？")</span><br><span class="line">guess = int(temp)</span><br><span class="line">if guess > 8:</span><br><span class="line"> print("大了，大了")</span><br><span class="line">else:</span><br><span class="line"> if guess == 8:</span><br><span class="line"> print("你太了解小姐姐的心思了！")</span><br><span class="line"> print("哼，猜对也没有奖励！")</span><br><span class="line"> else:</span><br><span class="line"> print("小了，小了")</span><br><span class="line">print("游戏结束，不玩儿啦！")</span><br><span class="line">猜一猜小姐姐想的是哪个数字？8</span><br><span class="line">你太了解小姐姐的心思了！</span><br><span class="line">哼，猜对也没有奖励！</span><br><span class="line">游戏结束，不玩儿啦！</span><br></pre></td></tr></table></figure><h2 id="3-if-elif-else-语句"><a href="#3-if-elif-else-语句" class="headerlink" title="3. if - elif - else 语句"></a>3. if - elif - else 语句</h2><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">if</span> expression1:</span><br><span class="line"> expr1_true_suite</span><br><span class="line"><span class="keyword">elif</span> expression2:</span><br><span class="line"> expr2_true_suite</span><br><span class="line"> .</span><br><span class="line"> .</span><br><span class="line"><span class="keyword">elif</span> expressionN:</span><br><span class="line"> exprN_true_suite</span><br><span class="line"><span class="keyword">else</span>:</span><br><span class="line"> expr_false_suite</span><br></pre></td></tr></table></figure><ul><li>elif 语句即为 else if，用来检查多个表达式是否为真，并在为真时执行特定代码块中的代码。</li></ul><p>【例子】</p><p>[42]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">temp = input('请输入成绩:')</span><br><span class="line">source = int(temp)</span><br><span class="line">if 100 >= source >= 90:</span><br><span class="line"> print('A')</span><br><span class="line">elif 90 > source >= 80:</span><br><span class="line"> print('B')</span><br><span class="line">elif 80 > source >= 60:</span><br><span class="line"> print('C')</span><br><span class="line">elif 60 > source >= 0:</span><br><span class="line"> print('D')</span><br><span class="line">else:</span><br><span class="line"> print('输入错误！')</span><br><span class="line">请输入成绩:99</span><br><span class="line">A</span><br></pre></td></tr></table></figure><h2 id="4-assert-关键词"><a href="#4-assert-关键词" class="headerlink" title="4. assert 关键词"></a>4. assert 关键词</h2><ul><li><code>assert</code>这个关键词我们称之为“断言”，当这个关键词后边的条件为 False 时，程序自动崩溃并抛出<code>AssertionError</code>的异常。</li></ul><p>【例子】</p><p>[ ]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">my_list = ['lsgogroup']</span><br><span class="line">my_list.pop(0)</span><br><span class="line">assert len(my_list) > 0</span><br><span class="line"></span><br><span class="line"># AssertionError</span><br></pre></td></tr></table></figure><p>【例子】在进行单元测试时，可以用来在程序中置入检查点，只有条件为 True 才能让程序正常工作。</p><p>[ ]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">assert 3 > 7</span><br><span class="line"></span><br><span class="line"># AssertionError</span><br></pre></td></tr></table></figure><h1 id="循环语句"><a href="#循环语句" class="headerlink" title="循环语句"></a>循环语句</h1><h2 id="1-while-循环"><a href="#1-while-循环" class="headerlink" title="1. while 循环"></a>1. while 循环</h2><p><code>while</code>语句最基本的形式包括一个位于顶部的布尔表达式，一个或多个属于<code>while</code>代码块的缩进语句。</p><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">while</span> 布尔表达式:</span><br><span class="line"> 代码块</span><br></pre></td></tr></table></figure><p><code>while</code>循环的代码块会一直循环执行，直到布尔表达式的值为布尔假。</p><p>如果布尔表达式不带有<code><、>、==、！=、in、not in</code>等运算符，仅仅给出数值之类的条件，也是可以的。当<code>while</code>后写入一个非零整数时，视为真值，执行循环体；写入<code>0</code>时，视为假值，不执行循环体。也可以写入<code>str、list</code>或任何序列，长度非零则视为真值，执行循环体；否则视为假值，不执行循环体。</p><p>【例子】</p><p>[44]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line">count = 0</span><br><span class="line">while count < 3:</span><br><span class="line"> temp = input("猜一猜小姐姐想的是哪个数字？")</span><br><span class="line"> guess = int(temp)</span><br><span class="line"> if guess > 8:</span><br><span class="line"> print("大了，大了")</span><br><span class="line"> else:</span><br><span class="line"> if guess == 8:</span><br><span class="line"> print("你太了解小姐姐的心思了！")</span><br><span class="line"> print("哼，猜对也没有奖励！")</span><br><span class="line"> count = 3</span><br><span class="line"> else:</span><br><span class="line"> print("小了，小了")</span><br><span class="line"> count = count + 1</span><br><span class="line">print("游戏结束，不玩儿啦！")</span><br><span class="line">猜一猜小姐姐想的是哪个数字？8</span><br><span class="line">你太了解小姐姐的心思了！</span><br><span class="line">哼，猜对也没有奖励！</span><br><span class="line">游戏结束，不玩儿啦！</span><br></pre></td></tr></table></figure><p>【例子】布尔表达式返回0，循环终止。</p><p>[45]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">string = 'abcd'</span><br><span class="line">while string:</span><br><span class="line"> print(string)</span><br><span class="line"> string = string[1:]</span><br><span class="line"></span><br><span class="line"># abcd</span><br><span class="line"># bcd</span><br><span class="line"># cd</span><br><span class="line"># d</span><br><span class="line">abcd</span><br><span class="line">bcd</span><br><span class="line">cd</span><br><span class="line">d</span><br></pre></td></tr></table></figure><hr><h2 id="2-while-else-循环"><a href="#2-while-else-循环" class="headerlink" title="2. while - else 循环"></a>2. while - else 循环</h2><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">while</span> 布尔表达式:</span><br><span class="line"> 代码块</span><br><span class="line"><span class="keyword">else</span>:</span><br><span class="line"> 代码块</span><br></pre></td></tr></table></figure><p>当<code>while</code>循环正常执行完的情况下，执行<code>else</code>输出，如果<code>while</code>循环中执行了跳出循环的语句，比如 <code>break</code>，将不执行<code>else</code>代码块的内容。</p><p>【例子】</p><p>[46]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line">count = 0</span><br><span class="line">while count < 5:</span><br><span class="line"> print("%d is less than 5" % count)</span><br><span class="line"> count = count + 1</span><br><span class="line">else:</span><br><span class="line"> print("%d is not less than 5" % count)</span><br><span class="line"> </span><br><span class="line"># 0 is less than 5</span><br><span class="line"># 1 is less than 5</span><br><span class="line"># 2 is less than 5</span><br><span class="line"># 3 is less than 5</span><br><span class="line"># 4 is less than 5</span><br><span class="line"># 5 is not less than 5</span><br><span class="line">0 is less than 5</span><br><span class="line">1 is less than 5</span><br><span class="line">2 is less than 5</span><br><span class="line">3 is less than 5</span><br><span class="line">4 is less than 5</span><br><span class="line">5 is not less than 5</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[47]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">count = 0</span><br><span class="line">while count < 5:</span><br><span class="line"> print("%d is less than 5" % count)</span><br><span class="line"> count = 6</span><br><span class="line"> break</span><br><span class="line">else:</span><br><span class="line"> print("%d is not less than 5" % count)</span><br><span class="line"></span><br><span class="line"># 0 is less than 5</span><br><span class="line">0 is less than 5</span><br></pre></td></tr></table></figure><hr><h2 id="3-for-循环"><a href="#3-for-循环" class="headerlink" title="3. for 循环"></a>3. for 循环</h2><p><code>for</code>循环是迭代循环，在Python中相当于一个通用的序列迭代器，可以遍历任何有序序列，如<code>str、list、tuple</code>等，也可以遍历任何可迭代对象，如<code>dict</code>。</p><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">for</span> 迭代变量 <span class="keyword">in</span> 可迭代对象:</span><br><span class="line"> 代码块</span><br></pre></td></tr></table></figure><p>每次循环，迭代变量被设置为可迭代对象的当前元素，提供给代码块使用。</p><p>【例子】</p><p>[48]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">for i in 'ILoveLSGO':</span><br><span class="line"> print(i, end=' ') # 不换行输出</span><br><span class="line"></span><br><span class="line"># I L o v e L S G O</span><br><span class="line">I L o v e L S G O</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[49]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line">member = ['张三', '李四', '刘德华', '刘六', '周润发']</span><br><span class="line">for each in member:</span><br><span class="line"> print(each)</span><br><span class="line"></span><br><span class="line"># 张三</span><br><span class="line"># 李四</span><br><span class="line"># 刘德华</span><br><span class="line"># 刘六</span><br><span class="line"># 周润发</span><br><span class="line"></span><br><span class="line">for i in range(len(member)):</span><br><span class="line"> print(member[i])</span><br><span class="line"></span><br><span class="line"># 张三</span><br><span class="line"># 李四</span><br><span class="line"># 刘德华</span><br><span class="line"># 刘六</span><br><span class="line"># 周润发</span><br><span class="line">张三</span><br><span class="line">李四</span><br><span class="line">刘德华</span><br><span class="line">刘六</span><br><span class="line">周润发</span><br><span class="line">张三</span><br><span class="line">李四</span><br><span class="line">刘德华</span><br><span class="line">刘六</span><br><span class="line">周润发</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[50]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">dic = {'a': 1, 'b': 2, 'c': 3, 'd': 4}</span><br><span class="line"></span><br><span class="line">for key, value in dic.items():</span><br><span class="line"> print(key, value, sep=':', end=' ')</span><br><span class="line"> </span><br><span class="line"># a:1 b:2 c:3 d:4 </span><br><span class="line">a:1 b:2 c:3 d:4</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[51]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">dic = {'a': 1, 'b': 2, 'c': 3, 'd': 4}</span><br><span class="line"></span><br><span class="line">for key in dic.keys():</span><br><span class="line"> print(key, end=' ')</span><br><span class="line"> </span><br><span class="line"># a b c d </span><br><span class="line">a b c d</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[52]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">dic = {'a': 1, 'b': 2, 'c': 3, 'd': 4}</span><br><span class="line"></span><br><span class="line">for value in dic.values():</span><br><span class="line"> print(value, end=' ')</span><br><span class="line"> </span><br><span class="line"># 1 2 3 4</span><br><span class="line">1 2 3 4</span><br></pre></td></tr></table></figure><hr><h2 id="4-for-else-循环"><a href="#4-for-else-循环" class="headerlink" title="4. for - else 循环"></a>4. for - else 循环</h2><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">for</span> 迭代变量 <span class="keyword">in</span> 可迭代对象:</span><br><span class="line"> 代码块</span><br><span class="line"><span class="keyword">else</span>:</span><br><span class="line"> 代码块</span><br></pre></td></tr></table></figure><p>当<code>for</code>循环正常执行完的情况下，执行<code>else</code>输出，如果<code>for</code>循环中执行了跳出循环的语句，比如 <code>break</code>，将不执行<code>else</code>代码块的内容，与<code>while - else</code>语句一样。</p><p>【例子】</p><p>[53]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line">for num in range(10, 20): # 迭代 10 到 20 之间的数字</span><br><span class="line"> for i in range(2, num): # 根据因子迭代</span><br><span class="line"> if num % i == 0: # 确定第一个因子</span><br><span class="line"> j = num / i # 计算第二个因子</span><br><span class="line"> print('%d 等于 %d * %d' % (num, i, j))</span><br><span class="line"> break # 跳出当前循环</span><br><span class="line"> else: # 循环的 else 部分</span><br><span class="line"> print(num, '是一个质数')</span><br><span class="line"></span><br><span class="line"># 10 等于 2 * 5</span><br><span class="line"># 11 是一个质数</span><br><span class="line"># 12 等于 2 * 6</span><br><span class="line"># 13 是一个质数</span><br><span class="line"># 14 等于 2 * 7</span><br><span class="line"># 15 等于 3 * 5</span><br><span class="line"># 16 等于 2 * 8</span><br><span class="line"># 17 是一个质数</span><br><span class="line"># 18 等于 2 * 9</span><br><span class="line"># 19 是一个质数</span><br><span class="line">10 等于 2 * 5</span><br><span class="line">11 是一个质数</span><br><span class="line">12 等于 2 * 6</span><br><span class="line">13 是一个质数</span><br><span class="line">14 等于 2 * 7</span><br><span class="line">15 等于 3 * 5</span><br><span class="line">16 等于 2 * 8</span><br><span class="line">17 是一个质数</span><br><span class="line">18 等于 2 * 9</span><br><span class="line">19 是一个质数</span><br></pre></td></tr></table></figure><hr><h2 id="5-range-函数"><a href="#5-range-函数" class="headerlink" title="5. range() 函数"></a>5. range() 函数</h2><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">range([start,] stop[, step=<span class="number">1</span>])</span><br></pre></td></tr></table></figure><ul><li>这个BIF（Built-in functions）有三个参数，其中用中括号括起来的两个表示这两个参数是可选的。</li><li><code>step=1</code> 表示第三个参数的默认值是1。</li><li><code>range</code> 这个BIF的作用是生成一个从<code>start</code>参数的值开始到<code>stop</code>参数的值结束的数字序列，该序列包含<code>start</code>的值但不包含<code>stop</code>的值。</li></ul><p>【例子】</p><p>[54]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">for i in range(2, 9): # 不包含9</span><br><span class="line"> print(i)</span><br><span class="line"></span><br><span class="line"># 2</span><br><span class="line"># 3</span><br><span class="line"># 4</span><br><span class="line"># 5</span><br><span class="line"># 6</span><br><span class="line"># 7</span><br><span class="line"># 8</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[55]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">for i in range(1, 10, 2):</span><br><span class="line"> print(i)</span><br><span class="line"></span><br><span class="line"># 1</span><br><span class="line"># 3</span><br><span class="line"># 5</span><br><span class="line"># 7</span><br><span class="line"># 9</span><br><span class="line">1</span><br><span class="line">3</span><br><span class="line">5</span><br><span class="line">7</span><br><span class="line">9</span><br></pre></td></tr></table></figure><hr><h2 id="6-enumerate-函数"><a href="#6-enumerate-函数" class="headerlink" title="6. enumerate()函数"></a>6. enumerate()函数</h2><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">enumerate(sequence, [start=<span class="number">0</span>])</span><br></pre></td></tr></table></figure><ul><li>sequence：一个序列、迭代器或其他支持迭代对象。</li><li>start：下标起始位置。</li><li>返回 enumerate(枚举) 对象</li></ul><p>【例子】</p><p>[56]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">seasons = ['Spring', 'Summer', 'Fall', 'Winter']</span><br><span class="line">lst = list(enumerate(seasons))</span><br><span class="line">print(lst)</span><br><span class="line"># [(0, 'Spring'), (1, 'Summer'), (2, 'Fall'), (3, 'Winter')]</span><br><span class="line">lst = list(enumerate(seasons, start=1)) # 下标从 1 开始</span><br><span class="line">print(lst)</span><br><span class="line"># [(1, 'Spring'), (2, 'Summer'), (3, 'Fall'), (4, 'Winter')]</span><br><span class="line">[(0, 'Spring'), (1, 'Summer'), (2, 'Fall'), (3, 'Winter')]</span><br><span class="line">[(1, 'Spring'), (2, 'Summer'), (3, 'Fall'), (4, 'Winter')]</span><br></pre></td></tr></table></figure><p><code>enumerate()</code>与 for 循环的结合使用。</p><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">for</span> i, a <span class="keyword">in</span> enumerate(A)</span><br><span class="line"> do something <span class="keyword">with</span> a</span><br></pre></td></tr></table></figure><p>用 <code>enumerate(A)</code> 不仅返回了 <code>A</code> 中的元素，还顺便给该元素一个索引值 (默认从 0 开始)。此外，用 <code>enumerate(A, j)</code> 还可以确定索引起始值为 <code>j</code>。</p><p>【例子】</p><p>[57]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line">languages = ['Python', 'R', 'Matlab', 'C++']</span><br><span class="line">for language in languages:</span><br><span class="line"> print('I love', language)</span><br><span class="line">print('Done!')</span><br><span class="line"># I love Python</span><br><span class="line"># I love R</span><br><span class="line"># I love Matlab</span><br><span class="line"># I love C++</span><br><span class="line"># Done!</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">for i, language in enumerate(languages, 2):</span><br><span class="line"> print(i, 'I love', language)</span><br><span class="line">print('Done!')</span><br><span class="line"># 2 I love Python</span><br><span class="line"># 3 I love R</span><br><span class="line"># 4 I love Matlab</span><br><span class="line"># 5 I love C++</span><br><span class="line"># Done!</span><br><span class="line">I love Python</span><br><span class="line">I love R</span><br><span class="line">I love Matlab</span><br><span class="line">I love C++</span><br><span class="line">Done!</span><br><span class="line">2 I love Python</span><br><span class="line">3 I love R</span><br><span class="line">4 I love Matlab</span><br><span class="line">5 I love C++</span><br><span class="line">Done!</span><br></pre></td></tr></table></figure><hr><h2 id="7-break-语句"><a href="#7-break-语句" class="headerlink" title="7. break 语句"></a>7. break 语句</h2><p><code>break</code>语句可以跳出当前所在层的循环。</p><p>【例子】</p><p>[59]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line">import random</span><br><span class="line">secret = random.randint(1, 10) #[1,10]之间的随机数</span><br><span class="line"></span><br><span class="line">while True:</span><br><span class="line"> temp = input("猜一猜小姐姐想的是哪个数字？")</span><br><span class="line"> guess = int(temp)</span><br><span class="line"> if guess > secret:</span><br><span class="line"> print("大了，大了")</span><br><span class="line"> else:</span><br><span class="line"> if guess == secret:</span><br><span class="line"> print("你太了解小姐姐的心思了！")</span><br><span class="line"> print("哼，猜对也没有奖励！")</span><br><span class="line"> break</span><br><span class="line"> else:</span><br><span class="line"> print("小了，小了")</span><br><span class="line">print("游戏结束，不玩儿啦！")</span><br><span class="line">猜一猜小姐姐想的是哪个数字？8</span><br><span class="line">你太了解小姐姐的心思了！</span><br><span class="line">哼，猜对也没有奖励！</span><br><span class="line">游戏结束，不玩儿啦！</span><br></pre></td></tr></table></figure><hr><h2 id="8-continue-语句"><a href="#8-continue-语句" class="headerlink" title="8. continue 语句"></a>8. continue 语句</h2><p><code>continue</code>终止本轮循环并开始下一轮循环。</p><p>【例子】</p><p>[60]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line">for i in range(10):</span><br><span class="line"> if i % 2 != 0:</span><br><span class="line"> print(i)</span><br><span class="line"> continue</span><br><span class="line"> i += 2</span><br><span class="line"> print(i)</span><br><span class="line"></span><br><span class="line"># 2</span><br><span class="line"># 1</span><br><span class="line"># 4</span><br><span class="line"># 3</span><br><span class="line"># 6</span><br><span class="line"># 5</span><br><span class="line"># 8</span><br><span class="line"># 7</span><br><span class="line"># 10</span><br><span class="line"># 9</span><br><span class="line">2</span><br><span class="line">1</span><br><span class="line">4</span><br><span class="line">3</span><br><span class="line">6</span><br><span class="line">5</span><br><span class="line">8</span><br><span class="line">7</span><br><span class="line">10</span><br><span class="line">9</span><br></pre></td></tr></table></figure><hr><h2 id="9-pass-语句"><a href="#9-pass-语句" class="headerlink" title="9. pass 语句"></a>9. pass 语句</h2><p><code>pass</code> 语句的意思是“不做任何事”，如果你在需要有语句的地方不写任何语句，那么解释器会提示出错，而 <code>pass</code> 语句就是用来解决这些问题的。</p><p>【例子】</p><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">def</span> <span class="title">a_func</span><span class="params">()</span>:</span></span><br><span class="line"></span><br><span class="line"><span class="comment"># SyntaxError: unexpected EOF while parsing</span></span><br></pre></td></tr></table></figure><p>【例子】</p><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">def</span> <span class="title">a_func</span><span class="params">()</span>:</span></span><br><span class="line"> <span class="keyword">pass</span></span><br></pre></td></tr></table></figure><p><code>pass</code>是空语句，不做任何操作，只起到占位的作用，其作用是为了保持程序结构的完整性。尽管<code>pass</code>语句不做任何操作，但如果暂时不确定要在一个位置放上什么样的代码，可以先放置一个<code>pass</code>语句，让代码可以正常运行。</p><hr><h2 id="10-推导式"><a href="#10-推导式" class="headerlink" title="10. 推导式"></a>10. 推导式</h2><p><strong>列表推导式</strong></p><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">[ expr <span class="keyword">for</span> value <span class="keyword">in</span> collection [<span class="keyword">if</span> condition] ]</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[61]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">x = [-4, -2, 0, 2, 4]</span><br><span class="line">y = [a * 2 for a in x]</span><br><span class="line">print(y)</span><br><span class="line"># [-8, -4, 0, 4, 8]</span><br><span class="line">[-8, -4, 0, 4, 8]</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[63]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">x = [i ** 2 for i in range(1, 10)]</span><br><span class="line">print(x)</span><br><span class="line"># [1, 4, 9, 16, 25, 36, 49, 64, 81]</span><br><span class="line">[1, 4, 9, 16, 25, 36, 49, 64, 81]</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[64]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">x = [(i, i ** 2) for i in range(6)]</span><br><span class="line">print(x)</span><br><span class="line"></span><br><span class="line"># [(0, 0), (1, 1), (2, 4), (3, 9), (4, 16), (5, 25)]</span><br><span class="line">[(0, 0), (1, 1), (2, 4), (3, 9), (4, 16), (5, 25)]</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[65]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">x = [i for i in range(100) if (i % 2) != 0 and (i % 3) == 0]</span><br><span class="line">print(x)</span><br><span class="line"></span><br><span class="line"># [3, 9, 15, 21, 27, 33, 39, 45, 51, 57, 63, 69, 75, 81, 87, 93, 99]</span><br><span class="line">[3, 9, 15, 21, 27, 33, 39, 45, 51, 57, 63, 69, 75, 81, 87, 93, 99]</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[66]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">a = [(i, j) for i in range(0, 3) for j in range(0, 3)]</span><br><span class="line">print(a)</span><br><span class="line"></span><br><span class="line"># [(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2), (2, 0), (2, 1), (2, 2)]</span><br><span class="line">[(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2), (2, 0), (2, 1), (2, 2)]</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[67]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">x = [[i, j] for i in range(0, 3) for j in range(0, 3)]</span><br><span class="line">print(x)</span><br><span class="line"># [[0, 0], [0, 1], [0, 2], [1, 0], [1, 1], [1, 2], [2, 0], [2, 1], [2, 2]]</span><br><span class="line"></span><br><span class="line">x[0][0] = 10</span><br><span class="line">print(x)</span><br><span class="line"># [[10, 0], [0, 1], [0, 2], [1, 0], [1, 1], [1, 2], [2, 0], [2, 1], [2, 2]]</span><br><span class="line">[[0, 0], [0, 1], [0, 2], [1, 0], [1, 1], [1, 2], [2, 0], [2, 1], [2, 2]]</span><br><span class="line">[[10, 0], [0, 1], [0, 2], [1, 0], [1, 1], [1, 2], [2, 0], [2, 1], [2, 2]]</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[68]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">a = [(i, j) for i in range(0, 3) if i < 1 for j in range(0, 3) if j > 1]</span><br><span class="line">print(a)</span><br><span class="line"></span><br><span class="line"># [(0, 2)]</span><br><span class="line">[(0, 2)]</span><br></pre></td></tr></table></figure><p><strong>元组推导式</strong></p><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">( expr <span class="keyword">for</span> value <span class="keyword">in</span> collection [<span class="keyword">if</span> condition] )</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[69]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">a = (x for x in range(10))</span><br><span class="line">print(a)</span><br><span class="line"></span><br><span class="line"># <generator object <genexpr> at 0x0000025BE511CC48></span><br><span class="line"></span><br><span class="line">print(tuple(a))</span><br><span class="line"></span><br><span class="line"># (0, 1, 2, 3, 4, 5, 6, 7, 8, 9)</span><br><span class="line"><generator object <genexpr> at 0x0000014CEC2E28B8></span><br><span class="line">(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)</span><br></pre></td></tr></table></figure><p><strong>字典推导式</strong></p><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">{ key_expr: value_expr <span class="keyword">for</span> value <span class="keyword">in</span> collection [<span class="keyword">if</span> condition] }</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[70]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">b = {i: i % 2 == 0 for i in range(10) if i % 3 == 0}</span><br><span class="line">print(b)</span><br><span class="line"># {0: True, 3: False, 6: True, 9: False}</span><br><span class="line">{0: True, 3: False, 6: True, 9: False}</span><br></pre></td></tr></table></figure><p><strong>集合推导式</strong></p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">{ expr for value in collection [if condition] }</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[71]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">c = {i for i in [1, 2, 3, 4, 5, 5, 6, 4, 3, 2, 1]}</span><br><span class="line">print(c)</span><br><span class="line"># {1, 2, 3, 4, 5, 6}</span><br><span class="line">{1, 2, 3, 4, 5, 6}</span><br></pre></td></tr></table></figure><p><strong>其它</strong></p><ul><li><code>next(iterator[, default])</code> Return the next item from the iterator. If default is given and the iterator is exhausted, it is returned instead of raising StopIteration.</li></ul><p>【例子】</p><p>[72]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">e = (i for i in range(10))</span><br><span class="line">print(e)</span><br><span class="line"># <generator object <genexpr> at 0x0000007A0B8D01B0></span><br><span class="line"></span><br><span class="line">print(next(e)) # 0</span><br><span class="line">print(next(e)) # 1</span><br><span class="line"></span><br><span class="line">for each in e:</span><br><span class="line"> print(each, end=' ')</span><br><span class="line"></span><br><span class="line"># 2 3 4 5 6 7 8 9</span><br><span class="line"><generator object <genexpr> at 0x0000014CEC389C78></span><br><span class="line">0</span><br><span class="line">1</span><br><span class="line">2 3 4 5 6 7 8 9</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[73]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">s = sum([i for i in range(101)])</span><br><span class="line">print(s) # 5050</span><br><span class="line">s = sum((i for i in range(101)))</span><br><span class="line">print(s) # 5050</span><br><span class="line">5050</span><br><span class="line">5050</span><br></pre></td></tr></table></figure><h1 id="异常处理"><a href="#异常处理" class="headerlink" title="异常处理"></a>异常处理</h1><p>异常就是运行期检测到的错误。计算机语言针对可能出现的错误定义了异常类型，某种错误引发对应的异常时，异常处理程序将被启动，从而恢复程序的正常运行。</p><h2 id="1-Python-标准异常总结"><a href="#1-Python-标准异常总结" class="headerlink" title="1. Python 标准异常总结"></a>1. Python 标准异常总结</h2><ul><li>BaseException：所有异常的 <strong>基类</strong></li><li>Exception：常规异常的 <strong>基类</strong></li><li>StandardError：所有的内建标准异常的基类</li><li>ArithmeticError：所有数值计算异常的基类</li><li>FloatingPointError：浮点计算异常</li><li>OverflowError：数值运算超出最大限制</li><li>ZeroDivisionError：除数为零</li><li>AssertionError：断言语句（assert）失败</li><li>AttributeError：尝试访问未知的对象属性</li><li>EOFError：没有内建输入，到达EOF标记</li><li>EnvironmentError：操作系统异常的基类</li><li>IOError：输入/输出操作失败</li><li>OSError：操作系统产生的异常（例如打开一个不存在的文件）</li><li>WindowsError：系统调用失败</li><li>ImportError：导入模块失败的时候</li><li>KeyboardInterrupt：用户中断执行</li><li>LookupError：无效数据查询的基类</li><li>IndexError：索引超出序列的范围</li><li>KeyError：字典中查找一个不存在的关键字</li><li>MemoryError：内存溢出（可通过删除对象释放内存）</li><li>NameError：尝试访问一个不存在的变量</li><li>UnboundLocalError：访问未初始化的本地变量</li><li>ReferenceError：弱引用试图访问已经垃圾回收了的对象</li><li>RuntimeError：一般的运行时异常</li><li>NotImplementedError：尚未实现的方法</li><li>SyntaxError：语法错误导致的异常</li><li>IndentationError：缩进错误导致的异常</li><li>TabError：Tab和空格混用</li><li>SystemError：一般的解释器系统异常</li><li>TypeError：不同类型间的无效操作</li><li>ValueError：传入无效的参数</li><li>UnicodeError：Unicode相关的异常</li><li>UnicodeDecodeError：Unicode解码时的异常</li><li>UnicodeEncodeError：Unicode编码错误导致的异常</li><li>UnicodeTranslateError：Unicode转换错误导致的异常</li></ul><p>异常体系内部有层次关系，Python异常体系中的部分关系如下所示：</p><p><img src="https://img-blog.csdnimg.cn/20200710131404548.png" alt="Image"></p><hr><h2 id="2-Python标准警告总结"><a href="#2-Python标准警告总结" class="headerlink" title="2. Python标准警告总结"></a>2. Python标准警告总结</h2><ul><li>Warning：警告的基类</li><li>DeprecationWarning：关于被弃用的特征的警告</li><li>FutureWarning：关于构造将来语义会有改变的警告</li><li>UserWarning：用户代码生成的警告</li><li>PendingDeprecationWarning：关于特性将会被废弃的警告</li><li>RuntimeWarning：可疑的运行时行为(runtime behavior)的警告</li><li>SyntaxWarning：可疑语法的警告</li><li>ImportWarning：用于在导入模块过程中触发的警告</li><li>UnicodeWarning：与Unicode相关的警告</li><li>BytesWarning：与字节或字节码相关的警告</li><li>ResourceWarning：与资源使用相关的警告</li></ul><hr><h2 id="3-try-except-语句"><a href="#3-try-except-语句" class="headerlink" title="3. try - except 语句"></a>3. try - except 语句</h2><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">try</span>:</span><br><span class="line"> 检测范围</span><br><span class="line"><span class="keyword">except</span> Exception[<span class="keyword">as</span> reason]:</span><br><span class="line"> 出现异常后的处理代码</span><br></pre></td></tr></table></figure><p>try 语句按照如下方式工作：</p><ul><li>首先，执行<code>try</code>子句（在关键字<code>try</code>和关键字<code>except</code>之间的语句）</li><li>如果没有异常发生，忽略<code>except</code>子句，<code>try</code>子句执行后结束。</li><li>如果在执行<code>try</code>子句的过程中发生了异常，那么<code>try</code>子句余下的部分将被忽略。如果异常的类型和<code>except</code>之后的名称相符，那么对应的<code>except</code>子句将被执行。最后执行<code>try - except</code>语句之后的代码。</li><li>如果一个异常没有与任何的<code>except</code>匹配，那么这个异常将会传递给上层的<code>try</code>中。</li></ul><p>【例子】</p><p>[2]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">try:</span><br><span class="line"> f = open('test.txt')</span><br><span class="line"> print(f.read())</span><br><span class="line"> f.close()</span><br><span class="line">except OSError:</span><br><span class="line"> print('打开文件出错')</span><br><span class="line"></span><br><span class="line"># 打开文件出错</span><br><span class="line">打开文件出错</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[3]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">try:</span><br><span class="line"> f = open('test.txt')</span><br><span class="line"> print(f.read())</span><br><span class="line"> f.close()</span><br><span class="line">except OSError as error:</span><br><span class="line"> print('打开文件出错\n原因是：' + str(error))</span><br><span class="line"></span><br><span class="line"># 打开文件出错</span><br><span class="line"># 原因是：[Errno 2] No such file or directory: 'test.txt'</span><br><span class="line">打开文件出错</span><br><span class="line">原因是：[Errno 2] No such file or directory: 'test.txt'</span><br></pre></td></tr></table></figure><p>一个<code>try</code>语句可能包含多个<code>except</code>子句，分别来处理不同的特定的异常。最多只有一个分支会被执行。</p><p>【例子】</p><p>[4]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">try:</span><br><span class="line"> int("abc")</span><br><span class="line"> s = 1 + '1'</span><br><span class="line"> f = open('test.txt')</span><br><span class="line"> print(f.read())</span><br><span class="line"> f.close()</span><br><span class="line">except OSError as error:</span><br><span class="line"> print('打开文件出错\n原因是：' + str(error))</span><br><span class="line">except TypeError as error:</span><br><span class="line"> print('类型出错\n原因是：' + str(error))</span><br><span class="line">except ValueError as error:</span><br><span class="line"> print('数值出错\n原因是：' + str(error))</span><br><span class="line"></span><br><span class="line"># 数值出错</span><br><span class="line"># 原因是：invalid literal for int() with base 10: 'abc'</span><br><span class="line">数值出错</span><br><span class="line">原因是：invalid literal for int() with base 10: 'abc'</span><br></pre></td></tr></table></figure><p>【例子】</p><p>[5]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">dict1 = {'a': 1, 'b': 2, 'v': 22}</span><br><span class="line">try:</span><br><span class="line"> x = dict1['y']</span><br><span class="line">except LookupError:</span><br><span class="line"> print('查询错误')</span><br><span class="line">except KeyError:</span><br><span class="line"> print('键错误')</span><br><span class="line">else:</span><br><span class="line"> print(x)</span><br><span class="line"></span><br><span class="line"># 查询错误</span><br><span class="line">查询错误</span><br></pre></td></tr></table></figure><p><code>try-except-else</code>语句尝试查询不在<code>dict</code>中的键值对，从而引发了异常。这一异常准确地说应属于<code>KeyError</code>，但由于<code>KeyError</code>是<code>LookupError</code>的子类，且将<code>LookupError</code>置于<code>KeyError</code>之前，因此程序优先执行该<code>except</code>代码块。所以，使用多个<code>except</code>代码块时，必须坚持对其规范排序，要从最具针对性的异常到最通用的异常。</p><p>【例子】</p><p>[6]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">dict1 = {'a': 1, 'b': 2, 'v': 22}</span><br><span class="line">try:</span><br><span class="line"> x = dict1['y']</span><br><span class="line">except KeyError:</span><br><span class="line"> print('键错误')</span><br><span class="line">except LookupError:</span><br><span class="line"> print('查询错误')</span><br><span class="line">else:</span><br><span class="line"> print(x)</span><br><span class="line"></span><br><span class="line"># 键错误</span><br><span class="line">键错误</span><br></pre></td></tr></table></figure><p>【例子】一个 <code>except</code> 子句可以同时处理多个异常，这些异常将被放在一个括号里成为一个元组。</p><p>[7]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">try:</span><br><span class="line"> s = 1 + '1'</span><br><span class="line"> int("abc")</span><br><span class="line"> f = open('test.txt')</span><br><span class="line"> print(f.read())</span><br><span class="line"> f.close()</span><br><span class="line">except (OSError, TypeError, ValueError) as error:</span><br><span class="line"> print('出错了！\n原因是：' + str(error))</span><br><span class="line"></span><br><span class="line"># 出错了！</span><br><span class="line"># 原因是：unsupported operand type(s) for +: 'int' and 'str'</span><br><span class="line">出错了！</span><br><span class="line">原因是：unsupported operand type(s) for +: 'int' and 'str'</span><br></pre></td></tr></table></figure><hr><h2 id="4-try-except-finally-语句"><a href="#4-try-except-finally-语句" class="headerlink" title="4. try - except - finally 语句"></a>4. try - except - finally 语句</h2><p>try: 检测范围 except Exception[as reason]: 出现异常后的处理代码 finally: 无论如何都会被执行的代码</p><p>不管<code>try</code>子句里面有没有发生异常，<code>finally</code>子句都会执行。</p><p>【例子】如果一个异常在<code>try</code>子句里被抛出，而又没有任何的<code>except</code>把它截住，那么这个异常会在<code>finally</code>子句执行后被抛出。</p><p>[10]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line">def divide(x, y):</span><br><span class="line"> try:</span><br><span class="line"> result = x / y</span><br><span class="line"> print("result is", result)</span><br><span class="line"> except ZeroDivisionError:</span><br><span class="line"> print("division by zero!")</span><br><span class="line"> finally:</span><br><span class="line"> print("executing finally clause")</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">divide(2, 1)</span><br><span class="line"># result is 2.0</span><br><span class="line"># executing finally clause</span><br><span class="line">divide(2, 0)</span><br><span class="line"># division by zero!</span><br><span class="line"># executing finally clause</span><br><span class="line">divide("2", "1")</span><br><span class="line"># executing finally clause</span><br><span class="line"># TypeError: unsupported operand type(s) for /: 'str' and 'str'</span><br><span class="line">result is 2.0</span><br><span class="line">executing finally clause</span><br><span class="line">division by zero!</span><br><span class="line">executing finally clause</span><br></pre></td></tr></table></figure><hr><h2 id="5-try-except-else-语句"><a href="#5-try-except-else-语句" class="headerlink" title="5. try - except - else 语句"></a>5. try - except - else 语句</h2><p>如果在<code>try</code>子句执行时没有发生异常，Python将执行<code>else</code>语句后的语句。</p><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">try</span>:</span><br><span class="line"> 检测范围</span><br><span class="line"><span class="keyword">except</span>:</span><br><span class="line"> 出现异常后的处理代码</span><br><span class="line"><span class="keyword">else</span>:</span><br><span class="line"> 如果没有异常执行这块代码</span><br></pre></td></tr></table></figure><p>使用<code>except</code>而不带任何异常类型，这不是一个很好的方式，我们不能通过该程序识别出具体的异常信息，因为它捕获所有的异常。</p><p>try: 检测范围 except(Exception1[, Exception2[,…ExceptionN]]]): 发生以上多个异常中的一个，执行这块代码 else: 如果没有异常执行这块代码</p><p>【例子】</p><p>[12]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">try:</span><br><span class="line"> fh = open("testfile.txt", "w")</span><br><span class="line"> fh.write("这是一个测试文件，用于测试异常!!")</span><br><span class="line">except IOError:</span><br><span class="line"> print("Error: 没有找到文件或读取文件失败")</span><br><span class="line">else:</span><br><span class="line"> print("内容写入文件成功")</span><br><span class="line"> fh.close()</span><br><span class="line"></span><br><span class="line"># 内容写入文件成功</span><br><span class="line">内容写入文件成功</span><br></pre></td></tr></table></figure><p>注意：<code>else</code>语句的存在必须以<code>except</code>语句的存在为前提，在没有<code>except</code>语句的<code>try</code>语句中使用<code>else</code>语句，会引发语法错误。</p><hr><h2 id="6-raise语句"><a href="#6-raise语句" class="headerlink" title="6. raise语句"></a>6. raise语句</h2><p>Python 使用<code>raise</code>语句抛出一个指定的异常。</p><p>【例子】</p><p>[13]:</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">try:</span><br><span class="line"> raise NameError('HiThere')</span><br><span class="line">except NameError:</span><br><span class="line"> print('An exception flew by!')</span><br><span class="line"> </span><br><span class="line"># An exception flew by!</span><br><span class="line">An exception flew by!</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html"><h1 id="Python入门-上"><a href="#Python入门-上" class="headerlink" title="Python入门(上)"></a>Python入门(上)</h1><p>[TOC]</p>
<h1 id="简介"><a href="#简介" </summary>
<category term="python基础" scheme="https://wicherqaq.github.io/categories/python%E5%9F%BA%E7%A1%80/"/>
</entry>
<entry>
<title>运算符优先级</title>
<link href="https://wicherqaq.github.io/2020/09/09/%E8%BF%90%E7%AE%97%E7%AC%A6%E4%BC%98%E5%85%88%E7%BA%A7/"/>
<id>https://wicherqaq.github.io/2020/09/09/%E8%BF%90%E7%AE%97%E7%AC%A6%E4%BC%98%E5%85%88%E7%BA%A7/</id>
<published>2020-09-09T07:55:29.000Z</published>
<updated>2020-09-09T08:20:05.843Z</updated>
<content type="html"><![CDATA[<table><thead><tr><th><strong>优先级</strong></th><th><strong>运算符</strong></th><th><strong>名称或含义</strong></th><th><strong>使用形式</strong></th><th><strong>结合方向</strong></th><th><strong>说明</strong></th></tr></thead><tbody><tr><td><strong>1</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td></td><td><strong>[]</strong></td><td>数组下标</td><td>数组名[常量表达式]</td><td>左到右</td><td>–</td></tr><tr><td><strong>()</strong></td><td>圆括号</td><td>(表达式）/函数名(形参表)</td><td>–</td><td></td><td></td></tr><tr><td><strong>.</strong></td><td>成员选择（对象）</td><td>对象.成员名</td><td>–</td><td></td><td></td></tr><tr><td><strong>-></strong></td><td>成员选择（指针）</td><td>对象指针->成员名</td><td>–</td><td></td><td></td></tr><tr><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><strong>2</strong></td><td><strong>-</strong></td><td>负号运算符</td><td>-表达式</td><td><strong>右到左</strong></td><td>单目运算符</td></tr><tr><td><strong>~</strong></td><td>按位取反运算符</td><td>~表达式</td><td></td><td></td><td></td></tr><tr><td><strong>++</strong></td><td>自增运算符</td><td>++变量名/变量名++</td><td></td><td></td><td></td></tr><tr><td><strong>–</strong></td><td>自减运算符</td><td>–变量名/变量名–</td><td></td><td></td><td></td></tr><tr><td>*****</td><td>取值运算符</td><td>*指针变量</td><td></td><td></td><td></td></tr><tr><td><strong>&</strong></td><td>取地址运算符</td><td>&变量名</td><td></td><td></td><td></td></tr><tr><td><strong>!</strong></td><td>逻辑非运算符</td><td>!表达式</td><td></td><td></td><td></td></tr><tr><td><strong>类型</strong></td><td>强制类型转换</td><td>(数据类型)表达式</td><td>–</td><td></td><td></td></tr><tr><td><strong>sizeof</strong></td><td>长度运算符</td><td>sizeof(表达式)</td><td>–</td><td></td><td></td></tr><tr><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><strong>3</strong></td><td><strong>/</strong></td><td>除</td><td>表达式/表达式</td><td>左到右</td><td>双目运算符</td></tr><tr><td>*****</td><td>乘</td><td>表达式*表达式</td><td></td><td></td><td></td></tr><tr><td><strong>%</strong></td><td>余数（取模）</td><td>整型表达式%整型表达式</td><td></td><td></td><td></td></tr><tr><td><strong>4</strong></td><td><strong><em>\</em>+**</strong></td><td>加</td><td>表达式+表达式</td><td>左到右</td><td>双目运算符</td></tr><tr><td><strong>-</strong></td><td>减</td><td>表达式-表达式</td><td></td><td></td><td></td></tr><tr><td><strong>5</strong></td><td><strong><em>\</em><<**</strong></td><td>左移</td><td>变量<<表达式</td><td>左到右</td><td>双目运算符</td></tr><tr><td><strong>>></strong></td><td>右移</td><td>变量>>表达式</td><td></td><td></td><td></td></tr><tr><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><strong>6</strong></td><td><strong><em>\</em>>**</strong></td><td>大于</td><td>表达式>表达式</td><td>左到右</td><td>双目运算符</td></tr><tr><td><strong>>=</strong></td><td>大于等于</td><td>表达式>=表达式</td><td></td><td></td><td></td></tr><tr><td><strong><</strong></td><td>小于</td><td>表达式<表达式</td><td></td><td></td><td></td></tr><tr><td><strong><=</strong></td><td>小于等于</td><td>表达式<=表达式</td><td></td><td></td><td></td></tr><tr><td><strong>7</strong></td><td><strong>==</strong></td><td>等于</td><td>表达式==表达式</td><td>左到右</td><td>双目运算符</td></tr><tr><td><strong>!=</strong></td><td>不等于</td><td>表达式!= 表达式</td><td></td><td></td><td></td></tr><tr><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><strong>8</strong></td><td><strong><em>\</em>&**</strong></td><td>按位与</td><td>表达式&表达式</td><td>左到右</td><td>双目运算符</td></tr><tr><td><strong>9</strong></td><td><strong><em>\</em>^**</strong></td><td>按位异或</td><td>表达式^表达式</td><td>左到右</td><td>双目运算符</td></tr><tr><td><strong>10</strong></td><td><strong><em>\</em>|**</strong></td><td>按位或</td><td>表达式|表达式</td><td>左到右</td><td>双目运算符</td></tr><tr><td><strong>11</strong></td><td><strong><em>\</em>&&**</strong></td><td>逻辑与</td><td>表达式&&表达式</td><td>左到右</td><td>双目运算符</td></tr><tr><td><strong>12</strong></td><td><strong><em>\</em>||**</strong></td><td>逻辑或</td><td>表达式||表达式</td><td>左到右</td><td>双目运算符</td></tr><tr><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><strong>13</strong></td><td><strong><em>\</em>?:**</strong></td><td>条件运算符</td><td>表达式1?表达式2: 表达式3</td><td><strong><em>\</em>右到左**</strong></td><td>三目运算符</td></tr><tr><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><strong>14</strong></td><td><strong><em>\</em>=**</strong></td><td>赋值运算符</td><td>变量=表达式</td><td><strong><em>\</em>右到左**</strong></td><td>–</td></tr><tr><td><strong>/=</strong></td><td>除后赋值</td><td>变量/=表达式</td><td>–</td><td></td><td></td></tr><tr><td><strong>*=</strong></td><td>乘后赋值</td><td>变量*=表达式</td><td>–</td><td></td><td></td></tr><tr><td><strong>%=</strong></td><td>取模后赋值</td><td>变量%=表达式</td><td>–</td><td></td><td></td></tr><tr><td><strong>+=</strong></td><td>加后赋值</td><td>变量+=表达式</td><td>–</td><td></td><td></td></tr><tr><td><strong>-=</strong></td><td>减后赋值</td><td>变量-=表达式</td><td>–</td><td></td><td></td></tr><tr><td><strong><<=</strong></td><td>左移后赋值</td><td>变量<<=表达式</td><td>–</td><td></td><td></td></tr><tr><td><strong>>>=</strong></td><td>右移后赋值</td><td>变量>>=表达式</td><td>–</td><td></td><td></td></tr><tr><td><strong>&=</strong></td><td>按位与后赋值</td><td>变量&=表达式</td><td>–</td><td></td><td></td></tr><tr><td><strong>^=</strong></td><td>按位异或后赋值</td><td>变量^=表达式</td><td>–</td><td></td><td></td></tr><tr><td><strong>|=</strong></td><td>按位或后赋值</td><td>变量|=表达式</td><td>–</td><td></td><td></td></tr><tr><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><strong>15</strong></td><td><strong>，</strong></td><td>逗号运算符</td><td>表达式,表达式,…</td><td>左到右</td><td>–</td></tr></tbody></table><h4 id="说明"><a href="#说明" class="headerlink" title="说明"></a>说明</h4><ul><li>同一优先级的运算符，运算次序由结合方向所决定。</li><li>简单记就是：！ > 算术运算符 > 关系运算符 > && > || > 赋值运算符</li></ul>]]></content>
<summary type="html"><table>
<thead>
<tr>
<th><strong>优先级</strong></th>
<th><strong>运算符</strong></th>
<th><strong>名称或含义</strong></th>
<th><strong>使用形式</strong></</summary>
</entry>
<entry>
<title>Hexo博客迁移</title>
<link href="https://wicherqaq.github.io/2020/09/03/Hexo%E5%8D%9A%E5%AE%A2%E8%BF%81%E7%A7%BB/"/>
<id>https://wicherqaq.github.io/2020/09/03/Hexo%E5%8D%9A%E5%AE%A2%E8%BF%81%E7%A7%BB/</id>
<published>2020-09-03T06:12:56.000Z</published>
<updated>2020-09-03T06:13:32.000Z</updated>
<content type="html"><![CDATA[<h4 id="环境安装"><a href="#环境安装" class="headerlink" title="环境安装"></a>环境安装</h4><ul><li>安装node.js</li><li>安装cmpn镜像源 <code>npm install -g cnpm --registery=https://registry.npm.taobao.org</code></li><li>安装hexo框架 <code>cnpm install -g hexo-cli</code>，并且利用<code>hexo -v</code>来验证</li></ul><h4 id="拷贝原始数据"><a href="#拷贝原始数据" class="headerlink" title="拷贝原始数据"></a>拷贝原始数据</h4><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"># 以下是需要拷贝的文件和目录</span><br><span class="line">_config.yml</span><br><span class="line">package.json</span><br><span class="line">scaffolds</span><br><span class="line">source</span><br><span class="line">themes</span><br></pre></td></tr></table></figure><h4 id="安装依赖模块"><a href="#安装依赖模块" class="headerlink" title="安装依赖模块"></a>安装依赖模块</h4><p>执行下面的命令之前，需要把以上拷贝的文件复制到新电脑的博客文件夹下，如<code>/blog</code>下</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">npm install</span><br><span class="line">npm install hexo-deployer-git --save</span><br><span class="line">npm install hexo-generator-feed --save</span><br><span class="line">npm install hexo-generator-sitemap --save</span><br></pre></td></tr></table></figure><h4 id="构建、运行、发布"><a href="#构建、运行、发布" class="headerlink" title="构建、运行、发布"></a>构建、运行、发布</h4><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">hexo g</span><br><span class="line">hexo s</span><br><span class="line">hexo d# 要求填写github或其他发布平台的账号密码</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html"><h4 id="环境安装"><a href="#环境安装" class="headerlink" title="环境安装"></a>环境安装</h4><ul>
<li>安装node.js</li>
<li>安装cmpn镜像源 <code>npm install -g cnpm -</summary>
<category term="Hexo" scheme="https://wicherqaq.github.io/tags/Hexo/"/>
</entry>
<entry>
<title>Linux的Shell编程</title>
<link href="https://wicherqaq.github.io/2020/09/03/Linux%E7%9A%84Shell%E7%BC%96%E7%A8%8B/"/>
<id>https://wicherqaq.github.io/2020/09/03/Linux%E7%9A%84Shell%E7%BC%96%E7%A8%8B/</id>
<published>2020-09-03T05:21:22.000Z</published>
<updated>2020-09-03T06:08:38.000Z</updated>
<content type="html"><![CDATA[<h4 id="Linux的Shell编程"><a href="#Linux的Shell编程" class="headerlink" title="Linux的Shell编程"></a>Linux的Shell编程</h4><p> Shell 编程一般指 shell 脚本编程。</p><h5 id="语法"><a href="#语法" class="headerlink" title="语法"></a>语法</h5><p>使用 vi 编辑器新建一个文件 hello.sh </p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#</span><span class="bash">!/bin/bash </span></span><br><span class="line">echo "Hello World !"</span><br></pre></td></tr></table></figure><h5 id="执行"><a href="#执行" class="headerlink" title="执行"></a>执行</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"># 方式1</span><br><span class="line">sh hello.sh</span><br><span class="line"></span><br><span class="line"># 方式2</span><br><span class="line">chmod +x ./hello.sh #使脚本具有执行权限</span><br><span class="line">./hello.sh #执行脚本</span><br></pre></td></tr></table></figure><h4 id="变量"><a href="#变量" class="headerlink" title="变量"></a>变量</h4><h5 id="局部变量"><a href="#局部变量" class="headerlink" title="局部变量"></a>局部变量</h5><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#</span><span class="bash">!/bin/bash</span></span><br><span class="line">str="hello"</span><br><span class="line">echo ${str}world</span><br></pre></td></tr></table></figure><h5 id="环境变量"><a href="#环境变量" class="headerlink" title="环境变量"></a>环境变量</h5><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">echo $PATH</span><br><span class="line">echo $HOME</span><br></pre></td></tr></table></figure><h4 id="特殊字符"><a href="#特殊字符" class="headerlink" title="特殊字符"></a>特殊字符</h4><table><thead><tr><th>$#</th><th>传递到脚本的参数个数</th></tr></thead><tbody><tr><td>$*</td><td>以一个单字符串显示所有向脚本传递的参数。</td></tr><tr><td>$$</td><td>脚本运行的当前进程 ID 号</td></tr><tr><td>$!</td><td>后台运行的最后一个进程的 ID 号</td></tr><tr><td>$@</td><td>与$*相同，但是使用时加引号，并在引号中返回每个参数。</td></tr><tr><td>$?</td><td>显示最后命令的退出状态。 0 表示没有错误，其他任何值表明有错误。</td></tr></tbody></table><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#</span><span class="bash">!/bin/bash</span></span><br><span class="line">echo "第一个参数为： $1";</span><br><span class="line">echo "参数个数为： $#";</span><br><span class="line">echo "传递的参数作为一个字符串显示： $*";</span><br></pre></td></tr></table></figure><p>执行: ./test.sh 1 2 3 </p><h4 id="运算符"><a href="#运算符" class="headerlink" title="运算符"></a>运算符</h4> <figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#</span><span class="bash">!/bin/bash</span></span><br><span class="line">a=1;</span><br><span class="line">b=2;</span><br><span class="line">echo `expr $a + $b`;</span><br><span class="line">echo $((a+b));</span><br><span class="line">echo $[a+b];</span><br></pre></td></tr></table></figure><h4 id="if语句"><a href="#if语句" class="headerlink" title="if语句"></a>if语句</h4> <figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#</span><span class="bash">!/bin/bash</span></span><br><span class="line">read -p "please input your name:" NAME ## read命令用于从控制台读取输入数据</span><br><span class="line"><span class="meta">#</span><span class="bash"><span class="comment"># printf '%s\n' $NAME</span></span></span><br><span class="line">if [ $NAME = root ]</span><br><span class="line">then</span><br><span class="line">echo "hello ${NAME}, welcome !"</span><br><span class="line">elif [ $NAME = itcast ]</span><br><span class="line">then</span><br><span class="line">echo "hello ${NAME}, welcome !"</span><br><span class="line">else</span><br><span class="line">echo "Get out Please!"</span><br><span class="line">fi</span><br></pre></td></tr></table></figure><h4 id="for语句"><a href="#for语句" class="headerlink" title="for语句"></a>for语句</h4><p>方式1：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#</span><span class="bash">!/bin/bash</span></span><br><span class="line">for N in 1 2 3 </span><br><span class="line">do</span><br><span class="line"> echo $N</span><br><span class="line">done</span><br></pre></td></tr></table></figure><p>方式2：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#</span><span class="bash">!/bin/bash</span></span><br><span class="line">for ((i = 0; i <= 5; i++)) </span><br><span class="line"> do </span><br><span class="line"> echo "welcome $i times" </span><br><span class="line"> done</span><br></pre></td></tr></table></figure><h4 id="函数"><a href="#函数" class="headerlink" title="函数"></a>函数</h4><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#</span><span class="bash">!/bin/bash</span></span><br><span class="line">funWithReturn(){</span><br><span class="line">echo "这个函数会对输入的两个数字进行相加运算..."</span><br><span class="line">echo "输入第一个数字: "</span><br><span class="line">read aNum</span><br><span class="line">echo "输入第二个数字: "</span><br><span class="line">read anotherNum</span><br><span class="line">echo "两个数字分别为 $aNum 和 $anotherNum !"</span><br><span class="line">return $(($aNum+$anotherNum))</span><br><span class="line">} </span><br><span class="line">funWithReturn</span><br><span class="line">echo "输入的两个数字之和为 $? !"</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html"><h4 id="Linux的Shell编程"><a href="#Linux的Shell编程" class="headerlink" title="Linux的Shell编程"></a>Linux的Shell编程</h4><p> Shell 编程一般指 shell 脚本编程。</</summary>
<category term="Linux" scheme="https://wicherqaq.github.io/tags/Linux/"/>
</entry>
<entry>
<title>树莓派开机发送ip地址到邮箱</title>
<link href="https://wicherqaq.github.io/2020/08/27/%E6%A0%91%E8%8E%93%E6%B4%BE%E5%BC%80%E6%9C%BA%E5%8F%91%E9%80%81ip%E5%9C%B0%E5%9D%80%E5%88%B0%E9%82%AE%E7%AE%B1/"/>
<id>https://wicherqaq.github.io/2020/08/27/%E6%A0%91%E8%8E%93%E6%B4%BE%E5%BC%80%E6%9C%BA%E5%8F%91%E9%80%81ip%E5%9C%B0%E5%9D%80%E5%88%B0%E9%82%AE%E7%AE%B1/</id>
<published>2020-08-27T01:27:59.000Z</published>
<updated>2020-08-27T01:55:40.000Z</updated>
<content type="html"><![CDATA[<h4 id="概述"><a href="#概述" class="headerlink" title="概述"></a>概述</h4><p>一直以来，获取树莓派的IP一直都是一个让人头疼的问题。因为可能会面对不同的场景，某些场景下真的不能判断哪个ip是树莓派的。由于公司局域网内的机器比较多，我用<strong>IP Scanner</strong>软件扫描局域网内的机器，并不知道哪个IP是树莓派的，一个个试过去也不太现实，因此<strong>利用开机脚本发送邮箱</strong>成了一个不错的解决方案。</p><p>下面我来介绍一下如何才能实现这个功能</p><h4 id="第一步、编写python脚本"><a href="#第一步、编写python脚本" class="headerlink" title="第一步、编写python脚本"></a>第一步、编写python脚本</h4><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br></pre></td><td class="code"><pre><span class="line">import socket</span><br><span class="line">import smtplib</span><br><span class="line">import time</span><br><span class="line">from email.mime.text import MIMEText</span><br><span class="line"></span><br><span class="line"># 校验当前计算机的网络是否可用，是否可以连外网</span><br><span class="line">def check_network():</span><br><span class="line"> while True:</span><br><span class="line"> try:</span><br><span class="line"> url = "www.baidu.com" </span><br><span class="line"> host = socket.gethostbyname(url)</span><br><span class="line"> socket.create_connection((host,80),2)</span><br><span class="line"> print("Network is Ready!")</span><br><span class="line"> break</span><br><span class="line"> except Exception as e:</span><br><span class="line"> print(e)</span><br><span class="line"> print("Network is not ready,Sleep 5s...")</span><br><span class="line"> time.sleep(5)</span><br><span class="line"> return True</span><br><span class="line"></span><br><span class="line"># 获取本机的IP地址</span><br><span class="line">def get_host_ip():</span><br><span class="line"> try:</span><br><span class="line"> s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)</span><br><span class="line"> s.connect(('8.8.8.8', 80))</span><br><span class="line"> ip = s.getsockname()[0]</span><br><span class="line"> finally:</span><br><span class="line"> s.close()</span><br><span class="line"></span><br><span class="line"> return ip</span><br><span class="line"></span><br><span class="line"># 发送邮件</span><br><span class="line">def send_email():</span><br><span class="line"> from_addr = "your email address@mail.com"</span><br><span class="line"> password = "your password"</span><br><span class="line"> smtp_server = 'smtp.163.com'</span><br><span class="line"> to_addr = "receive address"</span><br><span class="line"> msg = MIMEText('Your raspberry IP addr is:'+get_host_ip())</span><br><span class="line"> msg["Subject"] = "raspberry IP addr notify"</span><br><span class="line"> msg['from'] = from_addr</span><br><span class="line"> msg['to'] = to_addr</span><br><span class="line"> try:</span><br><span class="line"> server = smtplib.SMTP(smtp_server)</span><br><span class="line"> server.login(from_addr, password)</span><br><span class="line"> server.sendmail(from_addr, [to_addr], msg.as_string())</span><br><span class="line"> server.quit()</span><br><span class="line"> print('success')</span><br><span class="line"> except Exception as e:</span><br><span class="line"> print('Faild:%s' % e)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">if __name__ == '__main__':</span><br><span class="line"> check_network()</span><br><span class="line"> send_email()</span><br></pre></td></tr></table></figure><h4 id="第二部、编写shell脚本"><a href="#第二部、编写shell脚本" class="headerlink" title="第二部、编写shell脚本"></a>第二部、编写shell脚本</h4><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">// 以下操作都在/usr/local/src/raspberryIP下</span><br><span class="line">// 需要把上一步编写的python脚本放到该目录下</span><br><span class="line">cd /usr/local/src/raspberryIP</span><br></pre></td></tr></table></figure><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">// 创建一个*.sh可执行文件</span><br><span class="line">sudo vim clientStart.sh</span><br></pre></td></tr></table></figure><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">// 编写执行脚本</span><br><span class="line">cd /usr/local/src/raspberryIP</span><br><span class="line">sudo python raspberryIP.py</span><br></pre></td></tr></table></figure><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">// 保存后测试下是否可以执行</span><br><span class="line">./clientStart.sh</span><br></pre></td></tr></table></figure><h4 id="第三步、开机启动方法设置"><a href="#第三步、开机启动方法设置" class="headerlink" title="第三步、开机启动方法设置"></a>第三步、开机启动方法设置</h4><p>编辑/etc/rc.local文件，在rc.local文件里Exit 0 前加入</p><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">/usr/local/src/raspberryIP/clientStart.sh start</span><br></pre></td></tr></table></figure><p>至此，所有工作都已完成</p>]]></content>
<summary type="html"><h4 id="概述"><a href="#概述" class="headerlink" title="概述"></a>概述</h4><p>一直以来，获取树莓派的IP一直都是一个让人头疼的问题。因为可能会面对不同的场景，某些场景下真的不能判断哪个ip是树莓派的。由于公司局域网内的</summary>
<category term="树莓派" scheme="https://wicherqaq.github.io/tags/%E6%A0%91%E8%8E%93%E6%B4%BE/"/>
</entry>
<entry>
<title>Idea中git的使用</title>
<link href="https://wicherqaq.github.io/2020/08/01/Idea%E4%B8%ADgit%E7%9A%84%E4%BD%BF%E7%94%A8/"/>
<id>https://wicherqaq.github.io/2020/08/01/Idea%E4%B8%ADgit%E7%9A%84%E4%BD%BF%E7%94%A8/</id>
<published>2020-08-01T10:39:07.000Z</published>
<updated>2020-08-01T10:41:38.000Z</updated>
<content type="html"><![CDATA[<p>工作中多人使用<a href="http://lib.csdn.net/base/git" target="_blank" rel="noopener">版本控制</a>软件协作开发，常见的应用场景归纳如下：</p><p>假设小组中有两个人，组长小张，组员小袁</p><p>场景一：小张创建项目并提交到远程<a href="http://lib.csdn.net/base/git" target="_blank" rel="noopener">Git</a>仓库</p><p>场景二：小袁从远程<a href="http://lib.csdn.net/base/git" target="_blank" rel="noopener">Git</a>仓库上获取项目源码</p><p>场景三：小袁修改了部分源码，提交到远程仓库</p><p>场景四：小张从远程仓库获取小袁的提交</p><p>场景五：小袁接受了一个新功能的任务，创建了一个分支并在分支上开发</p><p>场景六：小袁把分支提交到远程Git仓库</p><p>场景七：小张获取小袁提交的分支</p><p>场景八：小张把分支合并到主干</p><h3 id="场景一：小张创建项目并提交到远程Git仓库"><a href="#场景一：小张创建项目并提交到远程Git仓库" class="headerlink" title="场景一：小张创建项目并提交到远程Git仓库"></a>场景一：小张创建项目并提交到远程Git仓库</h3><p>创建好项目，选择VCS - > Import into Version Control -> Create Git Repository</p><p><img src="http://img.blog.csdn.net/20160912161234797" alt="img"></p><p>接下来指定本地仓库的位置，按个人习惯指定即可，例如这里选择了项目源代码同目录</p><p><img src="http://img.blog.csdn.net/20160912161334752" alt="img"></p><p>点击OK后创建完成本地仓库，注意，这里仅仅是本地的。下面把项目源码添加到本地仓库。</p><p>下图是Git与提交有关的三个命令对应的操作，Add命令是把文件从IDE的工作目录添加到本地仓库的stage区，Commit命令把stage区的暂存文件提交到当前分支的仓库，并清空stage区。Push命令把本地仓库的提交同步到远程仓库。</p><p><img src="http://img.blog.csdn.net/20160912164147415" alt="img"></p><p>IDEA中对操作做了一定的简化，Commit和Push可以在一步中完成。</p><p>具体操作，在项目上点击右键，选择Git菜单</p><p><img src="http://img.blog.csdn.net/20160912165901032" alt="img"></p><p><img src="http://img.blog.csdn.net/20160912165911954" alt="img"></p><p><img src="http://img.blog.csdn.net/20160912165921938" alt="img"></p><p>因为是第一次提交，Push前需要指定远程仓库的地址。如下图，点击Define remote后，在弹出的窗口中输入远程仓库地址。</p><p><img src="http://img.blog.csdn.net/20160912165942829" alt="img"></p><h3 id="场景二：小袁从远程Git仓库上获取项目源码"><a href="#场景二：小袁从远程Git仓库上获取项目源码" class="headerlink" title="场景二：小袁从远程Git仓库上获取项目源码"></a>场景二：小袁从远程Git仓库上获取项目源码</h3><p>即克隆项目，操作如下：</p><p><img src="http://img.blog.csdn.net/20160912170148207" alt="img"></p><p>输入小张Push时填写的远程仓库地址</p><p><img src="http://img.blog.csdn.net/20160912170214880" alt="img"></p><p>接下来按向导操作，即可把项目从远程仓库克隆到本地仓库和IDE工作区。</p><h3 id="场景三：小袁修改了部分源码，提交到远程仓库"><a href="#场景三：小袁修改了部分源码，提交到远程仓库" class="headerlink" title="场景三：小袁修改了部分源码，提交到远程仓库"></a>场景三：小袁修改了部分源码，提交到远程仓库</h3><p>这个操作和首次提交的流程基本一致，分别是 Add -> Commit -> Push。请参考场景一</p><h3 id="场景四：小张从远程仓库获取小袁的提交"><a href="#场景四：小张从远程仓库获取小袁的提交" class="headerlink" title="场景四：小张从远程仓库获取小袁的提交"></a>场景四：小张从远程仓库获取小袁的提交</h3><p>获取更新有两个命令：Fetch和Pull，Fetch是从远程仓库下载文件到本地的origin/master，然后可以手动对比修改决定是否合并到本地的master库。Pull则是直接下载并合并。如果各成员在工作中都执行修改前先更新的规范，则可以直接使用Pull方式以简化操作。</p><p><img src="http://img.blog.csdn.net/20160912170628933" alt="img"></p><h3 id="场景五：小袁接受了一个新功能的任务，创建了一个分支并在分支上开发"><a href="#场景五：小袁接受了一个新功能的任务，创建了一个分支并在分支上开发" class="headerlink" title="场景五：小袁接受了一个新功能的任务，创建了一个分支并在分支上开发"></a>场景五：小袁接受了一个新功能的任务，创建了一个分支并在分支上开发</h3><p>建分支也是一个常用的操作，例如临时修改bug、开发不确定是否加入的功能等，都可以创建一个分支，再等待合适的时机合并到主干。</p><p>创建流程如下：</p><p><img src="http://img.blog.csdn.net/20160912171844429" alt="img"></p><p>选择New Branch并输入一个分支的名称</p><p><img src="http://img.blog.csdn.net/20160912171858663" alt="img"></p><p>创建完成后注意IDEA的右下角，如下图，Git: wangpangzi_branch表示已经自动切换到wangpangzi_branch分支，当前工作在这个分支上。</p><p>点击后弹出一个小窗口，在Local Branches中有其他可用的本地分支选项，点击后选择Checkout即可切换当前工作的分支(见场景7操作切换其他分支)。</p><p><img src="http://img.blog.csdn.net/20160912173123122" alt="img"></p><p>如下图，点击Checkout</p><p><img src="http://img.blog.csdn.net/20160912173307202" alt="img"></p><p>注意，这里创建的分支仅仅在本地仓库，如果想让组长小张获取到这个分支，还需要提交到远程仓库。</p><h3 id="场景六：小袁把分支提交到远程Git仓库"><a href="#场景六：小袁把分支提交到远程Git仓库" class="headerlink" title="场景六：小袁把分支提交到远程Git仓库"></a>场景六：小袁把分支提交到远程Git仓库</h3><p>切换到新建的分支，使用Push功能</p><p><img src="http://img.blog.csdn.net/20160912173718844" alt="img"></p><p><img src="http://img.blog.csdn.net/20160912174243815" alt="img"></p><h3 id="场景七：小张获取小袁提交的分支"><a href="#场景七：小张获取小袁提交的分支" class="headerlink" title="场景七：小张获取小袁提交的分支"></a>场景七：小张获取小袁提交的分支</h3><p>使用Pull功能打开更新窗口，点击Remote栏后面的刷新按钮，会在Branches to merge栏中刷新出新的分支。这里并不想做合并，所以不要选中任何分支，直接点击Pull按钮完成操作。</p><p><img src="http://img.blog.csdn.net/20160912174329143" alt="img"></p><p>更新后，再点击右下角，可以看到在Remote Branches区已经有了新的分支，点击后在弹出的子菜单中选择Checkout as new local branch，在本地仓库中创建该分支。完成后在Local Branches区也会出现该分支的选项，可以按上面的方法，点击后选择Checkout切换。</p><p><img src="http://img.blog.csdn.net/20160912174729488" alt="img"></p><h3 id="场景八：小张把分支合并到主干"><a href="#场景八：小张把分支合并到主干" class="headerlink" title="场景八：小张把分支合并到主干"></a>场景八：小张把分支合并到主干</h3><p>新功能开发完成，体验很好，项目组决定把该功能合并到主干上。</p><p>切换到master分支，选择Merge Changes</p><p><img src="http://img.blog.csdn.net/20160912175201306" alt="img"></p><p>选择要合并的分支，点击Merge完成</p><p><img src="http://img.blog.csdn.net/20160912175359903" alt="img"></p>]]></content>
<summary type="html"><p>工作中多人使用<a href="http://lib.csdn.net/base/git" target="_blank" rel="noopener">版本控制</a>软件协作开发，常见的应用场景归纳如下：</p>
<p>假设小组中有两个人，组长小张，组员小袁</p>
<</summary>
<category term="开发工具" scheme="https://wicherqaq.github.io/tags/%E5%BC%80%E5%8F%91%E5%B7%A5%E5%85%B7/"/>
</entry>
<entry>
<title>redis缓存穿透、缓存击穿、缓存雪崩</title>
<link href="https://wicherqaq.github.io/2020/06/01/redis%E7%BC%93%E5%AD%98%E7%A9%BF%E9%80%8F%E3%80%81%E7%BC%93%E5%AD%98%E5%87%BB%E7%A9%BF%E3%80%81%E7%BC%93%E5%AD%98%E9%9B%AA%E5%B4%A9/"/>
<id>https://wicherqaq.github.io/2020/06/01/redis%E7%BC%93%E5%AD%98%E7%A9%BF%E9%80%8F%E3%80%81%E7%BC%93%E5%AD%98%E5%87%BB%E7%A9%BF%E3%80%81%E7%BC%93%E5%AD%98%E9%9B%AA%E5%B4%A9/</id>
<published>2020-06-01T02:09:36.000Z</published>
<updated>2020-06-01T02:28:52.000Z</updated>
<content type="html"><![CDATA[<h3 id="概述"><a href="#概述" class="headerlink" title="概述"></a>概述</h3><p>随着互联网系统发展的逐步完善，提高系统的QPS（每秒查询率），目前的绝大部分系统都增加了<a href="http://mp.weixin.qq.com/s?__biz=MzU5NTAzNjM0Mw==&mid=2247484731&idx=2&sn=932f690ee1b775e864d3e113739a421a&chksm=fe7954e3c90eddf5d2f7de72909a43b5151797df7212b10311c497c3d1708d9a0613279f5734&scene=21#wechat_redirect" target="_blank" rel="noopener">缓存机制</a>从而避免请求过多的直接与数据库操作从而造成系统瓶颈，极大的提升了用户体验和系统稳定性。但同时，一个缓存机制的设计如果不是很好，就可能带来一些问题：<strong>缓存穿透、缓存击穿与缓存雪崩效应</strong>。这些问题的出现本质上都是在一定的条件下导致的数据库DB的访问量过高导致的系统QPS较低的问题。</p><p>前台请求，后台先从缓存中取数据，取到直接返回结果，取不到时从数据库中取，数据库取到更新缓存，并返回结果，数据库也没取到，那直接返回空结果。常见的缓存机制如下图：</p><img src="/2020/06/01/redis%E7%BC%93%E5%AD%98%E7%A9%BF%E9%80%8F%E3%80%81%E7%BC%93%E5%AD%98%E5%87%BB%E7%A9%BF%E3%80%81%E7%BC%93%E5%AD%98%E9%9B%AA%E5%B4%A9/缓存机制.png" style="zoom:60%;"><h3 id="缓存问题"><a href="#缓存问题" class="headerlink" title="缓存问题"></a>缓存问题</h3><h4 id="缓存穿透"><a href="#缓存穿透" class="headerlink" title="缓存穿透"></a>缓存穿透</h4><h5 id="描述"><a href="#描述" class="headerlink" title="描述"></a>描述</h5><p>缓存穿透是指<strong>缓存和数据库中都没有的数据</strong>，而用户不断发起请求。由于缓存是不命中时被动写的，并且出于容错考虑，如果从存储层查不到数据则不写入缓存，这将导致这个不存在的数据每次请求都要到存储层去查询，失去了缓存的意义。</p><p>在流量大时，可能DB就挂掉了，要是有人利用不存在的key频繁攻击我们的应用，这就是漏洞。</p><p>如发起为id为“-1”的数据或id为特别大不存在的数据。这时的用户很可能是攻击者，攻击会导致数据库压力过大。</p><h5 id="解决方案"><a href="#解决方案" class="headerlink" title="解决方案"></a>解决方案</h5><ol><li><strong>接口层增加校验</strong>，如用户鉴权校验，id做基础校验，id<=0的直接拦截；</li><li>从缓存取不到的数据，在数据库中也没有取到，这时也可以将key-value对写为<strong>key-null</strong>，<strong>缓存有效时间可以设置短点</strong>，如30秒（设置太长会导致正常情况也没法使用）。这样可以防止攻击用户反复用同一个id暴力攻击</li></ol><h4 id="缓存击穿"><a href="#缓存击穿" class="headerlink" title="缓存击穿"></a>缓存击穿</h4><h5 id="描述-1"><a href="#描述-1" class="headerlink" title="描述"></a>描述</h5><p><strong>缓存击穿是指缓存中没有但数据库中有的数据（一般是缓存时间到期）</strong>，这时由于并发用户特别多，同时读缓存没读到数据，又同时去数据库去取数据，引起数据库压力瞬间增大，造成过大压力。</p><h5 id="解决方案-1"><a href="#解决方案-1" class="headerlink" title="解决方案"></a>解决方案</h5><ol><li>设置热点数据永远不过期。</li><li>接口限流与熔断，降级。重要的接口一定要做好限流策略，防止用户恶意刷接口，同时要降级准备，当接口中的某些 服务 不可用时候，进行熔断，失败快速返回机制。</li><li>布隆过滤器。bloomfilter就类似于一个hash set，用于快速判某个元素是否存在于集合中，其典型的应用场景就是快速判断一个key是否存在于某容器，不存在就直接返回。布隆过滤器的关键就在于hash算法和容器大小，</li></ol><h4 id="缓存雪崩"><a href="#缓存雪崩" class="headerlink" title="缓存雪崩"></a>缓存雪崩</h4><h5 id="描述-2"><a href="#描述-2" class="headerlink" title="描述"></a>描述</h5><p>缓存雪崩是指缓存中数据大批量到过期时间，而查询数据量巨大，引起数据库压力过大甚至down机。和缓存击穿不同的是， 缓存击穿指并发查同一条数据，缓存雪崩是不同数据都过期了，很多数据都查不到从而查数据库。</p><h5 id="解决方案-2"><a href="#解决方案-2" class="headerlink" title="解决方案"></a>解决方案</h5><ol><li>缓存数据的过期时间设置随机，防止同一时间大量数据过期现象发生。</li><li>如果缓存数据库是分布式部署，将热点数据均匀分布在不同搞得缓存数据库中。</li><li>设置热点数据永远不过期。</li></ol>]]></content>
<summary type="html"><h3 id="概述"><a href="#概述" class="headerlink" title="概述"></a>概述</h3><p>随着互联网系统发展的逐步完善，提高系统的QPS（每秒查询率），目前的绝大部分系统都增加了<a href="http://mp.weixin.</summary>
<category term="Java面试题" scheme="https://wicherqaq.github.io/categories/Java%E9%9D%A2%E8%AF%95%E9%A2%98/"/>
</entry>
<entry>
<title>wget命令</title>
<link href="https://wicherqaq.github.io/2020/05/30/wget%E5%91%BD%E4%BB%A4/"/>
<id>https://wicherqaq.github.io/2020/05/30/wget%E5%91%BD%E4%BB%A4/</id>
<published>2020-05-30T04:01:02.000Z</published>
<updated>2020-05-30T04:13:32.000Z</updated>
<content type="html"><![CDATA[<h3 id="概述"><a href="#概述" class="headerlink" title="概述"></a>概述</h3><p>wget命令用来从指定的URL下载文件。wget非常稳定，它在带宽很窄的情况下和不稳定网络中有很强的适应性，如果是由于网络的原因下载失败，wget会不断的尝试，直到整个文件下载完毕。如果是服务器打断下载过程，它会再次联到服务器上从停止的地方继续下载。这对从那些限定了链接时间的服务器上下载大文件非常有用。</p><h3 id="语法"><a href="#语法" class="headerlink" title="语法"></a>语法</h3><ul><li><p><code>wget [选项] [参数]</code></p></li><li><p>参数</p><blockquote><table><thead><tr><th>选项</th><th>描述</th></tr></thead><tbody><tr><td>-a<日志文件></td><td>在指定的日志文件中记录资料的执行过程；</td></tr><tr><td>-A<后缀名></td><td>指定要下载文件的后缀名，多个后缀名之间使用逗号进行分隔；</td></tr><tr><td>-b</td><td>进行后台的方式运行wget；</td></tr><tr><td>-B<连接地址></td><td>设置参考的连接地址的基地地址；</td></tr><tr><td>-c</td><td>继续执行上次终端的任务；</td></tr><tr><td>-C<标志></td><td>设置服务器数据块功能标志on为激活，off为关闭，默认值为on；</td></tr><tr><td>-d</td><td>调试模式运行指令；</td></tr><tr><td>-D<域名列表></td><td>设置顺着的域名列表，域名之间用“，”分隔；</td></tr><tr><td>-e<指令></td><td>作为文件“.wgetrc”中的一部分执行指定的指令；</td></tr><tr><td>-h</td><td>显示指令帮助信息；</td></tr><tr><td>-i<文件></td><td>从指定文件获取要下载的URL地址；</td></tr><tr><td>-l<目录列表></td><td>设置顺着的目录列表，多个目录用“，”分隔；</td></tr><tr><td>-L</td><td>仅顺着关联的连接；</td></tr><tr><td>-r</td><td>递归下载方式；</td></tr><tr><td>-nc</td><td>文件存在时，下载文件不覆盖原有文件；</td></tr><tr><td>-nv</td><td>下载时只显示更新和出错信息，不显示指令的详细执行过程；</td></tr><tr><td>-q</td><td>不显示指令执行过程；</td></tr><tr><td>-nh</td><td>不查询主机名称；</td></tr><tr><td>-v</td><td>显示详细执行过程；</td></tr><tr><td>-V</td><td>显示版本信息；</td></tr><tr><td>–passive-ftp</td><td>使用被动模式PASV连接FTP服务器；</td></tr><tr><td>–follow-ftp</td><td>从HTML文件中下载FTP连接文件。</td></tr></tbody></table></blockquote></li></ul><h3 id="示例"><a href="#示例" class="headerlink" title="示例"></a>示例</h3><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line">wget http://test.com/testfile.zip ->下载指定文件到当前文件夹</span><br><span class="line">wget -O wordpress.zip http://test.com/download ->指定保存名字</span><br><span class="line">wget --limit-rate=300k http://www.linuxde.net/testfile.zip ->限制下载速度</span><br><span class="line">wget -c http://www.linuxde.net/testfile.zip ->断点续传</span><br><span class="line">wget -b http://www.linuxde.net/testfile.zip ->后台下载</span><br><span class="line"></span><br><span class="line"># 设置使用指定浏览器下载（伪装下载）</span><br><span class="line">wget --user-agent="Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.16 (KHTML, like Gecko) Chrome/10.0.648.204 Safari/534.16" http://www.linuxde.net/testfile.zip</span><br><span class="line"></span><br><span class="line">wget --spider url ->测试下载</span><br><span class="line">wget --tries=40 URL ->设置重试次数为40</span><br><span class="line">wget -i filelist.txt ->从filelist.txt获取下载地址</span><br><span class="line"></span><br><span class="line"># 镜像网站</span><br><span class="line"># --miror开户镜像下载。</span><br><span class="line"># -p下载所有为了html页面显示正常的文件。</span><br><span class="line"># --convert-links下载后，转换成本地的链接。</span><br><span class="line"># -P ./LOCAL保存所有文件和目录到本地指定目录</span><br><span class="line">wget --mirror -p --convert-links -P ./LOCAL URL</span><br><span class="line"></span><br><span class="line">wget --reject=gif ur ->下载一个网站，但你不希望下载图片，可以使用这条命令</span><br><span class="line">wget -o download.log URL ->把下载信息存入日志文件</span><br><span class="line">wget -Q5m -i filelist.txt ->限制总下载文件大小</span><br><span class="line">wget -r -A.pdf url ->下载指定格式文件</span><br><span class="line"></span><br><span class="line"># FTP下载</span><br><span class="line">wget ftp-url</span><br><span class="line">wget --ftp-user=USERNAME --ftp-password=PASSWORD url</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html"><h3 id="概述"><a href="#概述" class="headerlink" title="概述"></a>概述</h3><p>wget命令用来从指定的URL下载文件。wget非常稳定，它在带宽很窄的情况下和不稳定网络中有很强的适应性，如果是由于网络的原因下载失败，w</summary>
<category term="Linux命令" scheme="https://wicherqaq.github.io/categories/Linux%E5%91%BD%E4%BB%A4/"/>
</entry>
</feed>