Lesson 4.1: Defining Functions and Function Arguments

Introduction:
Functions in Python are reusable blocks of code that perform a specific task. Using functions helps make programs organized, modular, and easier to maintain. This lesson covers how to define functions, pass arguments, and return values.

1. Defining a Function:

• Use the def keyword to define a function.

• Syntax:

Example – Simple Function:

Output:

2. Function Arguments:

• Arguments allow passing data into functions for processing.

Example – Function with Arguments:

Output:

3. Returning Values from Functions:

• Use return to send a value back to the caller.

Example – Function Returning Value:

Output:

4. Types of Function Arguments:

• Positional Arguments: Values passed in order.

• Keyword Arguments: Values passed by specifying parameter names.

• Default Arguments: Parameters with default values.

• Variable-length Arguments: Using *args for multiple values and **kwargs for key-value pairs.

Example – Default Argument:

Practical Tips:

• Keep functions short and focused on a single task

• Use descriptive function and parameter names

• Avoid unnecessary global variables; prefer passing data through arguments

Learning Outcome of This Lesson:

• Understand how to define and call functions in Python

• Use arguments to pass data into functions

• Return values from functions to use results

• Apply different types of arguments effectively

• Write modular and reusable code using functions