Lesson 9 of 20 · Functions

Functions — Part 9

Define a set of steps once, use it many times.

What you'll learn

You will learn how to create reusable code with functions — define once, call many times.

Words to know

Function: A named block of code you can run whenever you want by writing its name and ().
Define: To create a function (with def). You define it once.
Call: To run a function by writing its name and (). Each call runs the function's code.

Your turn

📋 Show the steps

Press ▶ Run and see what the computer says!

1'def say_hi():' creates a function — think of it as teaching the computer a new trick called 'say_hi'.
2The indented line print('Hi!') is what the trick does. But it doesn't run yet — we've only defined it, not called it.
3say_hi() on lines 3 and 4 CALLS the function — it tells the computer: 'do that trick now!' It runs twice, so 'Hi!' appears twice.
4Functions are reusable! Define a function once, then call it as many times as you need. This saves you from repeating code.

Auto-run is on: change the code and the result updates by itself.

Auto-run

Output

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Check your understanding · 1 of 4

What does 'def' do in Python?

Check your understanding · 2 of 4

def greet(): print('Hi') How do you run this function?

Check your understanding · 3 of 4

Why use functions?

Check your understanding · 4 of 4

def add(a, b): return a + b What does add(2, 3) give?

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