Upgrading from Wizard to Inventor

So far, you have been using spells (commands) that other people wrote:

• print()
• input()
• range()

But what if you want to make your own spell? What if you want a command called greet_player()?

Defining a Function

We use the keyword def (short for “define”).

def greet_player():
    print("Welcome, brave adventurer!")
    print("Prepare for glory!")

Run this. … Nothing happened?

That’s because we only defined (created) the spell. We haven’t cast (called) it yet.

Calling the Function

To use it, we just type its name:

greet_player()

Output:

Welcome, brave adventurer!
Prepare for glory!

You can call it as many times as you want!

greet_player()
greet_player()

Functions with Ingredients (Arguments)

Some spells need ingredients. print() needs text. Your function can take ingredients too!

def greet(name):
    print("Hello", name)
    print("Nice to meet you.")

Now we pass the name when we call it:

greet("Elena")
greet("Sam")

Output:

Hello Elena
Nice to meet you.
Hello Sam
Nice to meet you.

Why Use Functions?

1. Laziness: Write code once, use it 100 times.
2. Organization: Groups related code together (like a chapter in a book).
3. Clarity: check_game_over() is easier to read than 10 lines of if/else code.

Try It Yourself

Write a function called double_number(number) that takes a number and prints the double of it (number * 2).

This post is part of the Python Basics for Kids series, based on “Python for Kids from 8 to 88”.