Python Level 6: Functions

Goal of this Level

Today you will learn to:

• What functions are
• How to create your own functions
• How to call functions
• What parameters are
• What return values (return) are

By the end, you will be able to write programs that are organized, shorter, and reusable.

Step 1: What is a Function?

A function is a block of code that performs a specific task.

Benefits:

• You can use the code multiple times
• Your program becomes more organized
• Large programs are split into smaller parts

Real-life example:

A coffee machine is like a function.

You press a button → coffee is made.

In programming:

You call a function → it executes code.

Step 2: Creating a Function

A function is created with def.

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

Explanation:

• def means define
• hello is the name of the function
• () are always included
• Indented code belongs to the function

Step 3: Calling a Function

To execute a function, you must call it.

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

hello()

Output:

Hello!

Step 4: Functions with Parameters

Parameters are information that a function receives.

def greeting(name):
    print("Hello", name)

greeting("Anna")
greeting("Max")

Output:

Hello Anna
Hello Max

Explanation:

• name is the parameter
• "Anna" is the value passed

Step 5: Return Values

Sometimes a function should return a result.

For that, use return.

def greeting(name):
    return "Hello " + name

print(greeting("Anna"))

Output:

Hello Anna

Explanation:

• return returns a result
• The result can then be used further

Step 6: Function with Calculation

Functions are very useful for math or calculations.

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

print(add(3, 4))

Output:

7

Explanation:

• a and b are parameters
• return gives back the sum

Practice Example

def greeting(name):
    return "Hello " + name

print(greeting("Anna"))

What happens here:

• The function is created
• The name "Anna" is passed
• The function generates the text
• The result is printed

More Examples

Example 1:

def square(number):
    return number * number

print(square(5))

Output:

25

Example 2:

def welcome(name, age):
    print("Hello", name)
    print("You are", age, "years old")

welcome("Max", 20)

Task

Write a function that adds two numbers and returns the result.

Steps:

• Create the function
• Use two parameters
• Add the numbers
• Return the result

Example structure:

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

print(add_numbers(5, 3))

Output:

8