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Appendix A |
Python has several different versions and a number of ways it can be set up on each operating system. This section will help you install Python if the simple approach in Chapter 1 didn't work, or if you want to install a different version of Python than the one that came with your system.
Python is included by default on almost every Linux system, but you might want to use a different version than the default. If so, first find out which version of Python you already have installed:
$ python --version
Python 2.7.6
This shows that the default version is Python 2.7.6. However, you might have a version of Python 3 installed as well. To check, issue the following command:
$ python3 --version
Python 3.10
Python 3.10 is also installed. It's worth running both commands before you attempt to install a new version.
If you don't have Python 3 or if you want to install a newer version of Python 3, you can use a package called deadsnakes, which makes it easy to install multiple versions of Python:
sudo add-apt-repository ppa:deadsnakes/nightly
sudo apt update
sudo apt-get update
sudo apt-get install python3.10
These commands will install Python 3.10 to your system. The following command will start a terminal session running Python 3.10:
$ python3.10
>>>
You'll also use this command when you configure your text editor to use Python 3, and when you run programs from a terminal.
Python is already installed on most OS X systems, but you might want to use a different version than what's installed by default. First, find out which version of Python you already have installed:
$ python --version
Python 2.7.6
This shows that the default version is Python 2.7.6. However, you might have a version of Python 3 installed as well. To check, issue the command python3 --version. You'll probably get an error message, but it's worth checking to see if the version you want is already installed.
If you only have Python 2 installed, or if you have an older version of Python 3, you can install the latest version of Python 3 using a package called Homebrew.
Homebrew depends on Apple's Xcode package, so open a terminal and run the following command:
$ xcode-select --install
xcode-select: note: install requested for command line developer tools
Click through the confirmation dialogs that pop up. Next, install Homebrew with the following command:
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"Make sure you include a space between curl -fsSL and the URL. The -c in this command tells bash (the default shell for macOS) to execute the code that's downloaded here. You should only run commands like this from sources you trust.
To confirm that Homebrew was installed correctly, run the following command:
$ brew doctor
Your system is ready to brew.
This output means you're ready to install Python packages through Homebrew.
To install the latest version of Python 3, enter the following:
$ brew install python3
You can check which version was installed:
$ python3 --version
Python 3.10
$
Now you can start a Python 3 terminal session using the command python3, and you can ues the python3 command to configure your text editor so it runs Python programs with Python 3 instead of Python 2.
Python isn't usually included by default on Windows, but it's worth checking to see if it exists on your system. Open a command window and run the following command:
> python --version
Python 3.10
If you see output like this, Python is already installed, but you might want to install a newer version if your version is not up to date. If you see an error message, you'll need to download and install Python.
If you don't have Python 3 or if you want to install a newer version of Python 3, you can use a tool called pyenv, which makes it easy to install multiple versions of Python in Windows.
The easiest way is to first install Chocolatey package manager for Windows and then to install pyenv-win.
To install Chocolatey package manager, open an elevated PowerShell session ("Run as administrator") and use the following command in that session:
Set-ExecutionPolicy Bypass -Scope Process -Force; [System.Net.ServicePointManager]::SecurityProtocol = [System.Net.ServicePointManager]::SecurityProtocol -bor 3072; iex ((New-Object System.Net.WebClient).DownloadString('https://chocolatey.org/install.ps1'))Then, in the same elevated session, install pyenv-win using:
choco install pyenv-winLastly, to actually get Python installed, again in the elevated session, run:
pyenv install -l
These commands will install Python 3.10 to your system. The following command will start a terminal session running Python 3.10:
$ python3.10
>>>
You'll also use this command when you configure your text editor to use Python 3, and when you run programs from a terminal.
Close your PowerShell window and open a new one. This will load the new Path variable into your terminal session. Now when you enter python --version, you should see the version of Python you just set in your Path variable. You can now start a Python shell session by just entering python at a command prompt.