Lesson 9 – Functions

A function is a reusable block of code that performs a specific task. Instead of writing the same code again and again, you write it once inside a function and call it whenever needed. Functions help make your programs organised, cleaner, and easier to maintain.

What Does a Function Look Like?

A function has two parts: 1. Definition – where you create the function 2. Call – where you tell Python to run it

Example 1: A Simple Function

def greet():
    print("Hello, welcome to Python!")

greet()

Output:

Hello, welcome to Python!

Example 2: Function With Parameters

Parameters let your function receive information.

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

result = add(5, 3)
print(result)

Output:

Example 3: Function Returning Text

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

print(welcome("Khalid"))

Output:

Hello Khalid

Why Use Functions?

They reduce repetition in your code.
They make programs easier to read and understand.
They help organise large programs into small pieces.
They allow you to reuse the same code in many places.

Quiz: Test Your Understanding

1. What is a function?

A type of variable
A loop that repeats code
A reusable block of code
A Python library

Correct answer: A reusable block of code

2. What keyword is used to create a function?

func
def
create
make

Correct answer: def

3. What does a return statement do?

Stops the program
Sends a value back from a function
Prints text on the screen
Makes a loop repeat

Correct answer: Sends a value back from a function

4. What will this print?

def test(x):
    return x * 2

print(test(4))

2
4
6
8

Correct answer: 8

5. What is the output of this code?

def hello():
    print("Hi")

hello()

hello
Hi
error
nothing

Correct answer: Hi

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