beginner

Basic Function Definition

Create a simple function that returns a greeting.

Functions are reusable blocks of code that perform specific tasks. They help organize code, avoid repetition, and make programs more modular and maintainable.

📚 Concepts & Theory

Functions in Python are defined using the def keyword, followed by the function name, parentheses, and a colon. The function body is indented.

Basic Function Syntax:

def function_name():

    # function body

    return value

Function Components:

def keyword: Declares a function

Function name: Should be descriptive (use snake_case)

Parentheses (): Hold parameters (empty if none)

Colon : Starts the function body

Indentation: Defines the function scope

return statement: Sends value back to caller

Simple Example:

def greet():

    return "Hello, World!"

message = greet()  # Calls the function

print(message)  # "Hello, World!"

Functions Without Return:

def print_message():

    print("This function doesn't return anything")

    # Implicitly returns None

Why Use Functions:

Code Reusability: Write once, use many times

Organization: Break complex problems into smaller parts

Readability: Named functions describe what they do

Testing: Easier to test isolated functions

Maintenance: Change logic in one place

Function Naming Conventions:

Use lowercase with underscores (snake_case)

Be descriptive: calculate_total() not calc()

Verbs for actions: get_user(), send_email()

Understanding Return:
The return statement exits the function and sends a value back:

def add_five(n):

    return n + 5  # Exits here, sends result back

result = add_five(10)  # result = 15

Functions are fundamental to writing clean, maintainable Python code.

🎯 Your Challenge

Create a function named greet() that returns the string "Hello, World!"

📝 Starter Code

Python

def greet():
    pass

Start with the def keyword
Function name should be greet with empty parentheses
The function body must be indented
Use return to send back a value
Return the exact string: Hello, World!

Solution

Python

def greet():
    return "Hello, World!"

Explanation

The function uses the return statement to send back the string "Hello, World!" to the caller. When you call greet(), it executes the function body and returns this exact string. The return keyword is crucial—without it, the function would return None by default. This demonstrates the fundamental structure of Python functions: definition with def, function name, empty parameters, and a return value.

⚠️ Common Mistakes to Avoid

Forgetting the return statement (function returns None)
Not calling the function with parentheses ()
Indentation errors in function body
Using print() instead of return
Forgetting the colon after function definition

❓ Frequently Asked Questions

The function returns None by default. Always use return to send values back.

Yes! greet is the function object, greet() calls it and executes the code.

Yes! Use return a, b, c which returns a tuple.

return sends a value back to the caller. print() displays to console but doesn't return anything useful.

📚 Concepts & Theory

🎯 Your Challenge

📝 Starter Code

Solution

Explanation

⚠️ Common Mistakes to Avoid

❓ Frequently Asked Questions

🔗 Related Exercises

Arrow Functions

Function Basics

Function with Parameters

Understanding Return Values