Functions

A function is a reusable recipe. You write the steps once after def and give it a name; after that, you run all those steps just by calling the name. A parameter lets you hand the function different information each time, so one greet function can welcome any player. Writing a function does not run it; calling it does.

• Define a function with def and run it by calling its name.
• Pass information into a function using a parameter.
• Explain why functions save you from repeating code.
• Fix a function call that is missing its argument.

function

A named block of code you can run again and again by calling its name.

def

The keyword that creates a new function.

parameter

An input a function takes, listed inside its parentheses.

call

To run a function by writing its name with parentheses, like greet("Alex").

Edit the starter code below and press Run to see it work. Use Reset starter code to go back to the original at any time.

Expected output

Welcome, Alex!
Score: 0
Score: 10

Write a new function called game_over() that prints Thanks for playing! and call it at the end of the program.

This stops with an error about a missing argument. The greet function asks for a player in its parentheses. Look at the last line - what did the call forget to give it?

Broken code

def greet(player):
    print(f"Welcome, {player}!")

greet()

Give the function a value when you call it:
greet("Alex")

Write a function next_level(level) that prints a line like You reached level 5! using the number you pass in, then call it with a few different levels.

You wrote show_score once and used it twice. In your final game, what is something you will do more than once that could become a function?

Facilitating this lesson? See the teacher & librarian guide for how to run it, common mistakes, and an offline backup activity.