Manipulating Strings

Escape characters

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

# Escape characters: use backslash to insert special characters
# \n = newline, \' = single quote
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.

# Raw string (r prefix): treats backslashes as literal characters
print(r"Hello there!\nHow are you?\nI\'m doing fine.")  # \n printed literally

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

# String indexing: access characters by position (0-based)
spam = 'Hello world!'

spam[0]  # Returns first character: 'H'

'H'

spam[4]

'o'

spam[-1]

'!'

Slicing

# String slicing: extract substring using [start:end] syntax
spam = 'Hello world!'

spam[0:5]  # Returns characters from index 0 to 4: 'Hello'

'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 occurrences 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

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

8

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'

Relevant links

• format()
• len()
• str()
• repr()
• input()
• String Formatting
• Regular Expressions