Comprehensions

Python Medium · Lesson 1 · On the house

Comprehensions

Build a list in one honest line. Lesson 1 is free — on the house.

Lessons · Python Medium · Lesson 1 of 10 · On the house

Comprehensions

Build a list in one honest line.

Illustration for the Python course — Lesson 1 is on the house. The rest opens with the paper, the Daily, or a gift.

This is Python · medium, lesson 1: Comprehensions. Read the teaching and the stills before the checks. The quizzes are open book and test the subject — Python itself — not product rules or layout trivia.

You already know Introductory and Easy. Medium assumes those habits and asks for sharper tools.

[n * n for n in range(4)] builds [0, 1, 4, 9].

Add if filters after the iterable.

Nested comprehensions exist — prefer clarity.

Generator expressions use parentheses and stay lazy.

comp

squares = [n * n for n in range(4)]
print(squares)

Match this when you type. Open book.

Sit with that still. Trace it top to bottom. Name each piece. The exercise asks you to match its essence.

If something fails when you try it yourself, change one thing. Read the error. Return to the still. I will not rush you.

Quiz

What is [n * n for n in range(4)]?

[0, 1, 4, 9]
[1, 4, 9, 16]
[0, 1, 2, 3]
16

Quiz

What does a comprehension replace well?

A small loop that builds a list
Import statements
File deletion
Class inheritance

Quiz

How do you filter in a comprehension?

Add if after the iterable
Only with while
Only with goto
You cannot

Quiz

Based on today's teaching, which claim is right?

0²..3².
The opposite of what the lesson said
The lesson forbade this topic
None of the subject material applies

Quiz

Based on today's teaching, which claim is right?

List building.
The opposite of what the lesson said
The lesson forbade this topic
None of the subject material applies

Quiz

Based on today's teaching, which claim is right?

if clause filters.
The opposite of what the lesson said
The lesson forbade this topic
None of the subject material applies

Quiz

Based on today's teaching, which claim is right?

0²..3².
The opposite of what the lesson said
The lesson forbade this topic
None of the subject material applies

Quiz

Based on today's teaching, which claim is right?

List building.
The opposite of what the lesson said
The lesson forbade this topic
None of the subject material applies

Check

Match the still for: Comprehensions.

That is the lesson. When every quiz and exercise on this page is green, mark it passed. Next lesson when you are ready.

Open-book: the answers are on this page. Pass every quiz and check (9) to mark the lesson done. This visit: 0/9.

Comprehensions · Python Medium (free) — The Gold Standard