Functions in Python are reusable blocks of code that perform specific tasks. They help organize code, reduce repetition, and make programs more modular and easier to maintain.

1. What is a Function?

A function is a block of organized, reusable code designed to perform a single, related action. Python provides two types of functions:

• Built-in functions: Predefined functions like print(), len(), etc.
• User-defined functions: Functions that you define yourself using the def keyword.

2. Why Use Functions?

• Code Reusability: Write once, and reuse multiple times.
• Improved Readability: Simplify complex programs by breaking them into smaller, understandable parts.
• Maintainability: Easier to debug and modify.
• Avoid Redundancy: Reduce repetitive code.

3. Creating a Function

Syntax

def function_name(parameters):
    """
    Optional docstring: Explains what the function does.
    """
    # Function body
    return output # Optional

• def: Keyword used to define a function.
• function_name: Name of the function, which follows Python’s naming conventions.
• parameters: Variables passed into the function (optional).
• return: Specifies the output of the function (optional).

Examples of Functions

Example 1: A Simple Function

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

# Calling the function
welcome()

Example 2: Function with Parameters

def welcome_user(name):
print(f"Hello, {name}! Welcome to Python!")

# Calling the function with an argument
welcome_user("Infovistar")

5. Function with Return Value

A function can return a result using the return statement.

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

# Call the function and store the result
result = add_numbers(5, 3)
print("The sum is:", result)

By mastering functions, you’ll write cleaner, more efficient, and more scalable Python programs!