manipulating-strings.md

title	description
Manipulating strings - Python Cheatsheet	An escape character is created by typing a backslash \ followed by the character you want to insert.

Manipulating Strings

Escape characters

An escape character is created by typing a backslash \ followed by the character you want to insert.

Escape character	Prints as
\'	Single quote
\"	Double quote
\t	Tab
\n	Newline (line break)
\\	Backslash
\b	Backspace
\ooo	Octal value
\r	Carriage Return

>>> print("Hello there!\nHow are you?\nI\'m doing fine.")
# Hello there!
# How are you?
# I'm doing fine.

Raw strings

A raw string entirely ignores all escape characters and prints any backslash that appears in the string.

>>> print(r"Hello there!\nHow are you?\nI\'m doing fine.")
# Hello there!\nHow are you?\nI\'m doing fine.

Raw strings are mostly used for regular expression definition.

Multiline Strings with triple quotes

>>> print(
... """Dear Alice,
...
... Eve's cat has been arrested for catnapping,
... cat burglary, and extortion.
...
... Sincerely,
... Bob"""
... )

# Dear Alice,

# Eve's cat has been arrested for catnapping,
# cat burglary, and extortion.

# Sincerely,
# Bob

Indexing and Slicing strings

H   e   l   l   o       w   o   r   l   d    !
0   1   2   3   4   5   6   7   8   9   10   11

Indexing

>>> spam = 'Hello world!'

>>> spam[0]
# 'H'

>>> spam[4]
# 'o'

>>> spam[-1]
# '!'

Slicing

>>> spam = 'Hello world!'

>>> spam[0:5]
# 'Hello'

>>> spam[:5]
# 'Hello'

>>> spam[6:]
# 'world!'

>>> spam[6:-1]
# 'world'

>>> spam[:-1]
# 'Hello world'

>>> spam[::-1]
# '!dlrow olleH'

>>> fizz = spam[0:5]
>>> fizz
# 'Hello'

The in and not in operators

>>> 'Hello' in 'Hello World'
# True

>>> 'Hello' in 'Hello'
# True

>>> 'HELLO' in 'Hello World'
# False

>>> '' in 'spam'
# True

>>> 'cats' not in 'cats and dogs'
# False

upper() and lower() methods

Transforms a string to upper and lower case:

>>> greet = 'Hello world!'
>>> greet = greet.upper()
>>> greet
# 'HELLO WORLD!'

>>> greet = greet.lower()
>>> greet
# 'hello world!'

isupper() and islower() methods

Returns True or False after evaluating if a string is in upper or lower case:

>>> spam = 'Hello world!'
>>> spam.islower()
# False

>>> spam.isupper()
# False

>>> 'HELLO'.isupper()
# True

>>> 'abc12345'.islower()
# True

>>> '12345'.islower()
# False

>>> '12345'.isupper()
# False

The isX string methods

Method	Description
isalpha()	returns True if the string consists only of letters.
isalnum()	returns True if the string consists only of letters and numbers.
isdecimal()	returns True if the string consists only of numbers.
isspace()	returns True if the string consists only of spaces, tabs, and new-lines.
istitle()	returns True if the string consists only of words that begin with an uppercase letter followed by only lowercase characters.

The startswith() and endswith() methods

>>> 'Hello world!'.startswith('Hello')
# True

>>> 'Hello world!'.endswith('world!')
# True

>>> 'abc123'.startswith('abcdef')
# False

>>> 'abc123'.endswith('12')
# False

>>> 'Hello world!'.startswith('Hello world!')
# True

>>> 'Hello world!'.endswith('Hello world!')
# True

The join() and split() string methods

join()

The join() method takes all the items in an iterable, like a list, dictionary, tuple or set, and joins them into a string. You can also specify a separator.

>>> ''.join(['My', 'name', 'is', 'Simon'])
'MynameisSimon'

>>> ', '.join(['cats', 'rats', 'bats'])
# 'cats, rats, bats'

>>> ' '.join(['My', 'name', 'is', 'Simon'])
# 'My name is Simon'

>>> 'ABC'.join(['My', 'name', 'is', 'Simon'])
# 'MyABCnameABCisABCSimon'

split()

The split() method splits a string into a list. By default, it will use spaces to separate the items, but you can also set another character of choice:

>>> 'My name is Simon'.split()
# ['My', 'name', 'is', 'Simon']

>>> 'MyABCnameABCisABCSimon'.split('ABC')
# ['My', 'name', 'is', 'Simon']

>>> 'My name is Simon'.split('m')
# ['My na', 'e is Si', 'on']

Justifying text with rjust(), ljust() and center()

>>> 'Hello'.rjust(10)
# '     Hello'

>>> 'Hello'.rjust(20)
# '               Hello'

>>> 'Hello World'.rjust(20)
# '         Hello World'

>>> 'Hello'.ljust(10)
# 'Hello     '

>>> 'Hello'.center(20)
# '       Hello       '

An optional second argument to rjust() and ljust() will specify a fill character apart from a space character:

>>> 'Hello'.rjust(20, '*')
# '***************Hello'

>>> 'Hello'.ljust(20, '-')
# 'Hello---------------'

>>> 'Hello'.center(20, '=')
# '=======Hello========'

Removing whitespace with strip(), rstrip(), and lstrip()

>>> spam = '    Hello World     '
>>> spam.strip()
# 'Hello World'

>>> spam.lstrip()
# 'Hello World '

>>> spam.rstrip()
# '    Hello World'

>>> spam = 'SpamSpamBaconSpamEggsSpamSpam'
>>> spam.strip('ampS')
# 'BaconSpamEggs'