Functions: Your Own Commands

Create reusable commands with def, give them inputs and get answers back with return.

🎯 What you will learn

print() and len() are functions someone else built. Now YOU get to invent commands! Functions let you write code once and use it again and again. 🛠️

1. 🛠️ def

def makes a function. The indented code runs when you call it.

def cheer():
    print("Go team! 📣")

cheer()
cheer()

2. 📥 Parameters

Parameters let you send information in.

def greet(name):
    print("Hello, " + name + "!")

greet("Ana")
greet("Raj")

3. 📤 return

return sends an answer back.

def double(n):
    return n * 2

print(double(21))

Change the code and press ▶ Run to see what happens. You can’t break anything!

def to_fahrenheit(celsius):
    return celsius * 9 / 5 + 32

for c in [0, 20, 37, 100]:
    print(c, "°C =", to_fahrenheit(c), "°F")

def area(width, height):
    return width * height

result = area(4, 5)
print(result)

Tap a card to flip it over!

Write a function square(n) that returns n times n. The code below should print 49.

def square(n):
    

print(square(7))