Book: Fluent Python Author: Luciano Ramalho Excerpt: Chapter 2, List Comprehensions and Generator Expressions

List comprehensions are a more readable way to make a list than appending elements to a list with for loops. This is because for loops can be used for many different tasks but list comprehensions are only used for one thing - building lists. Their intent is explicit.

List Comprehension Syntax

[list_element for thing in things]

You can initialise other types of sequence with generator expressions

Generator Expressions

The syntax is the same a list comprehensions but with normal parentheses instead of square brackets.

For example for a Tuple:

tuple(list_element for thing in things)

Using a generator expression to make tuples over a list comprehension and for loop saves memory because it yields items one by one using the iterator protocol instead of making a whole list to store in memory to be iterated over.