Defining Functions

Introduction

A function is a reusable block of code that performs a specific task. Instead of writing the same logic in multiple places, you define it once and call it whenever you need it.

Basic Syntax

def function_name():
    # code to run when the function is called

Example

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

greet()   # Hello, World!
greet()   # Hello, World!

Naming Conventions

Function names follow the same rules as variables — lowercase with underscores (snake_case).

def calculate_salary():
    ...

def get_employee_name():
    ...

Docstrings

A docstring is a string at the top of a function that describes what it does. It is good practice to include one.

def greet():
    """Print a greeting message to the terminal."""
    print("Hello, World!")

Practice Exercises

• Define a function called print_header that prints a decorative line of = characters.
• Call it three times and verify it prints the same output each time.
• Add a docstring to your function describing what it does.