Vivienne Reay

Functions

A function is like a recipe that you write once and can use over and over again. Instead of writing the same instructions every time, you just call your function by name.

Defining a function

To create a function, use def, give it a name, add brackets, and a colon. Everything inside must be indented (pushed in).

def say_hello():
    print("Hello!")

Calling a function

To use a function, write its name followed by brackets:

say_hello()

This will run the code inside and print "Hello!".

Parameters and arguments

Functions can accept input values. Think of it like giving your recipe ingredients.

• Parameters are the ingredient names in your recipe.
• Arguments are the actual ingredients you use.

def greet(name):
    print("Hi, " + name)

greet("Alice")

Here, name is the parameter (the placeholder). When you call the function, "Alice" is the argument (the actual value).

Return values

A function can give you back a value using return. This lets you save the result and use it later.

def add_numbers(a, b):
    return a + b

answer = add_numbers(3, 5)
print(answer)  # Shows 8

The function calculates 3 + 5 and gives back 8, which you store in answer.