Strings in 5 minutes

Textual information in Python is handled by a str object. Strings are immutable and are written in three distinct ways:

Using single quotes: 'Hey you!'
Using double quotes: "Hey you!"
Using trippled single ou double quotes: """Hey you!""", '''Hey you'''

Single quote strings allows embedded double quote strings: 'embedded "double quotes"'. In the same way, double quote strings allows embedded single quote strings: "embedded 'single quotes'".

Trippled quoted strings are also known as raw strings because they can span multiple lines. For instance you can write:

>>> msg = "Hello\nworld"
>>> print(msg)
Hello
world

Or alternatively using raw strings:

>>> msg = """Hello
... world"""
>>> print(msg)
Hello
world

Strings that are part of a single expression separated only by whitespaces will be converted to a string.

>>> msg = ("hello " "world")
>>> print(msg)
hello world

Formatting strings

Python provides several ways to format strings, but the quick an easiest way to do it is by using f-strings. By using f-strings you are able do embed values to your string:

>>> what = "world"
>>> msg = f"Hello {what}"
>>> print(msg)
Hello world

Note that f-strings begin with an f and we use curly braces to wrap the variables which we want to embed the value in the target string.

Slicing

Since strings are sequences, we can use slice operations to return a range of characters by using the slice syntax. To do so, we need to specify the start and end position separated by a colon:

>>> msg = "Hello world"
>>> print(msg[0:5])
Hello

Note that the starting position is inclusive and the ending position is exclusive, which means in practice that the above example is slicing the string from position 0 up to position 4.

You can also specify a third parameter to the slicing syntax which will be assumed as a step. The below slice could be read as: from 0 up to 10 every two chars.

>>> msg = "Hello world"
>>> print(msg[0:11:2])
Hlowrd
>>>

By omitting the starting position, Python will assume 0. By omitting the ending position, Python will assume that you want to slice up to the end of the string.

>>> msg = "Hello world"
>>> print(msg[:5])
Hello
>>> print(msg[6:])
world

You can use negative index to specify characters from the end of the string to the beginning of the string, -1 meaning the last character, -2 meaning the second-to-last, and so on.

>>> msg = "Hello world"
>>> print(msg[:-1])
Hello worl
>>> print(msg[:-2])
Hello wor

The slicing syntax provide us the most badass way to reverse a string:

>>> msg = "reverse this"
>>> print(msg[::-1])
siht esrever