Lessons

Lessons

List Comprehensions

Step 1 of 8

The old way vs the Python way

Want to double every number in a list? Here's the traditional way — a loop, an empty list, and an append.

Run this. It works, but it's 4 lines for something simple. Python has a one-liner for this.

Output

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Build lists in one line. The most Pythonic feature — write less, do more.

This interactive Python tutorial has 8 hands-on exercises. Estimated time: 14 minutes.

The old way vs the Python way — Want to double every number in a list? Here's the traditional way — a loop, an empty list, and an append.
Your first list comprehension — Same result, one line:
Filtering with if — Add `if` at the end to filter: `[x for x in list if condition]`
Transform + filter together — You can transform AND filter in one comprehension.
Strings work too — Comprehensions work on any iterable — including strings.
Dictionary comprehensions — Same idea, but with `{key: value for ...}` — builds a dict instead of a list.
Set comprehensions — Use `{expression for ...}` (no colon) for a set — a collection with no duplicates.
Build a grade filter 🎓 — Given a dict of student scores, use comprehensions to:

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