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Lesson 4: Functions and Modular Programming | Coding Class Series

Introduction

Welcome to Lesson 4!
In this lesson, we will learn about functions – reusable blocks of code – and how to organize your program into modules. Functions make your code cleaner, easier to read, and maintainable.

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What is a Function?

A function is a block of code that performs a specific task. You can call it whenever you need to perform that task.

Example in Python:

def greet(name):
    print(f"Hello, {name}!")

greet("Alice")  # Output: Hello, Alice!
greet("Bob")    # Output: Hello, Bob!

Explanation:

• def greet(name): → defines a function named greet with a parameter name.
• print(f"Hello, {name}!") → code inside the function.
• greet("Alice") → calls the function with argument "Alice".

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Benefits of Functions

1. Reusability: Write once, use many times.
2. Readability: Makes code organized and easier to understand.
3. Debugging: Easy to test and fix small blocks of code.

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Modular Programming

Modular programming is the practice of splitting your code into multiple files or modules. Each module has a specific purpose, making your program scalable and easier to maintain.

Example:

• math_utils.py → contains functions for math operations
• main.py → calls functions from math_utils.py

# math_utils.py
def add(a, b):
    return a + b

def subtract(a, b):
    return a - b

# main.py
from math_utils import add, subtract

print(add(5, 3))      # Output: 8
print(subtract(5, 3)) # Output: 2

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Practice Exercises

1. Write a function to calculate the factorial of a number.
2. Create a function to check if a string is a palindrome.
3. Write a module string_utils.py containing functions: reverse_string(), count_vowels().
4. Import the module in another file and test all the functions.

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