Manipulating Strings

Escape characters

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

>>> 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

>>> 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(), lower() and title()

Transforms a string to upper, lower and title case:

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

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

>>> greet.title()
# '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

startswith() and endswith()

>>> '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

join() and split()

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 whitespace 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']

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

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

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'

The Count Method

Counts the number of occurences of a given character or substring in the string it is applied to. Can be optionally provided start and end index.

>>> sentence = 'one sheep two sheep three sheep four'
>>> sentence.count('sheep')
# 3

>>> sentence.count('e')
# 9

>>> sentence.count('e', 6)
# 8
# returns count of e after 'one sh' i.e 6 chars since beginning of string

>>> sentence.count('e', 7)
# 7

Replace Method

Replaces all occurences of a given substring with another substring. Can be optionally provided a third argument to limit the number of replacements. Returns a new string.

>>> text = "Hello, world!"
>>> text.replace("world", "planet")
# 'Hello, planet!'

>>> fruits = "apple, banana, cherry, apple"
>>> fruits.replace("apple", "orange", 1)
# 'orange, banana, cherry, apple'

>>> sentence = "I like apples, Apples are my favorite fruit"
>>> sentence.replace("apples", "oranges")
# 'I like oranges, Apples are my favorite fruit'