Learn Python · lesson 23 of 24

Functions that decide

Write is_even(n) that returns True for even numbers and False for odd ones, then use it in a loop to print the even numbers from 1 to 6.

Learn

A function can hold an if, and return True or False. Programmers call this a test function. is_even(n) can return n % 2 == 0, which is itself True or False. Then you can use it anywhere, even in a loop.

Your task

Write is_even(n) that returns True for even numbers and False for odd ones, then use it in a loop to print the even numbers from 1 to 6.

← Giving a function information Project: a quiz scorer →

Python

Press Run to see what your program prints.

Keep going in Learn Python

Functions: your own instructions

Write a function called cheer that prints Hip hip hooray! and call it twice.

Start →22

Giving a function information

Write a function double that returns its input times 2, and print double(21).

Start →24

Project: a quiz scorer

Write a function score(answers) that counts how many answers equal "yes", then print the result as You scored 3 out of 5 (use the length of the list for the out of number).

Start →

Practise the idea

🧱 Play Code Builder

The lines of a Python program are mixed up. Tap them into the right order, press Run and see if it works.

Play now

FAQ

Functions that decide: common questions

I am stuck. What can I do?

Press Hint for a nudge, read the message next to each goal, and compare your code with the lesson text. If you still need it, Show answer reveals a model solution. Try to type it yourself rather than copy it.

Does my work get saved?

Your ticks and XP are saved in this browser, and in your account if you log in. The code you type is not stored on a server.

Start a conversation

Enjoying coding? Meet a teacher.

Tell us the learner's age, country and what they would like to build, and we will suggest a class. A parent or guardian can make the enquiry.

Tell us the learner’s age or grade and goals
We’ll suggest a suitable class or learning path
We’ll confirm format, timing and fees with a parent or guardian

Play it, don't just read it

Write some code right now

Free games that need no sign-up. Pick one and play for five minutes.

All free games →

Pick a game

Today's maths challengeFive questions · the same for everyone today · keep your streak goingPlay