Python Basics · Data Structures · Lesson 19 of 36
List Comprehensions
Concept
List Comprehensions
A list comprehension builds a new list in one concise line, combining a loop and a condition.
Under the hood it's equivalent to a for loop that appends to a new list, just written more compactly and often considered more "Pythonic."
By the end of this lesson
- Explain the core idea behind List Comprehensions.
- Predict output before running a change.
- Test one realistic and one unusual input.
- Use the result to make the next decision.
How to study this page
- 1. Read one concept.
- 2. Change the example.
- 3. Run, compare, and explain.
- 4. Complete the challenge below.
Syntax
[expression for item in iterable if condition]ExampleRunnable
squares = [n * n for n in range(1, 6)]
evens = [n for n in range(20) if n % 2 == 0]
print(squares, evens)Self-check before continuing
Without looking at the example, describe what changes when you modify one input in List Comprehensions. Then reopen the editor and prove your explanation with a small test.
You are ready to continue when you can predict, test, and explain the result.
Your turn
Write a list comprehension that returns only the even numbers from a list.
Loading editor…
Console