Strings

Quotes

Text goes in quotes. Single and double do exactly the same thing:

first = "Ada"
second = 'Lovelace'
print(first, second)

Ada Lovelace

Having both is useful, because it lets you put one kind inside the other without any escaping:

print("it's fine")
print('she said "hello"')

it's fine
she said "hello"

Triple quotes span lines

note = """Dear Ada,
The engine works.
"""
print(note)

Dear Ada,
The engine works.

The line breaks you type are part of the string, which is why the output ends with a blank line — there is a newline before the closing quotes.

Length and indexing

len() counts characters. Indexing pulls one out, counting from zero:

word = "python"
print(len(word))
print(word[0])
print(word[5])

6
p
n

Negative indexes count from the right, which saves the arithmetic:

word = "python"
print(word[-1])
print(word[-2])

n
o

Strings never change

This is the property that explains most string behaviour. A string cannot be edited in place:

word = "python"
print(word.upper())
print(word)

PYTHON
python

upper() did not change word. It built a new string and handed it back. If you want to keep the result, assign it:

word = "python"
word = word.upper()
print(word)

PYTHON

Trying to edit in place is an error rather than a surprise, which is at least honest:

word = "python"
word[0] = "P"   # TypeError: 'str' object does not support item assignment

Looping over a string

A string is a sequence, so for walks its characters:

for letter in "abc":
    print(letter)

a
b
c

Checking what is inside

in asks about substrings, not just single characters:

sentence = "the quick brown fox"
print("quick" in sentence)
print("slow" in sentence)
print("Quick" in sentence)

True
False
False

The last one is False because comparison is case sensitive. Lowercase both sides when you do not care:

sentence = "the quick brown fox"
print("Quick".lower() in sentence.lower())

True