Scripts vs Modules¶

Python files can serve two different roles:

• scripts
• modules

Understanding this distinction helps structure programs effectively.

flowchart TD
    A[Python file]
    A --> B[Script]
    A --> C[Module]

1. What Is a Script?¶

A script is a program intended to be executed directly.

Example:

print("Hello, world")

Running the file executes the code immediately.

Scripts are commonly used for:

• automation
• quick utilities
• data processing tasks

2. What Is a Module?¶

A module is a file designed primarily for reuse.

It provides functions, classes, or variables that other programs import.

Example module:

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

Used in another file:

import math_utils

3. Scripts and Modules Together¶

A Python file can act as both a script and a module.

This is typically done with the main guard.

def greet():
    print("hello")

if __name__ == "__main__":
    greet()

4. Organizing Larger Programs¶

Programs often consist of many modules.

flowchart TD
    A[Main Script]
    A --> B[module A]
    A --> C[module B]
    A --> D[module C]

This modular structure improves readability and maintainability.

5. Advantages of Modules¶

Modules provide several benefits:

• code reuse
• separation of concerns
• easier debugging
• clearer program organization

Large software systems rely heavily on modular structure.

6. Worked Example¶

File math_utils.py

def square(x):
    return x * x

Main script:

import math_utils

print(math_utils.square(6))

Output:

36

7. Summary¶

Key ideas:

• scripts are programs executed directly
• modules contain reusable definitions
• Python files can serve both roles
• modular design improves program structure

Modules are essential for building larger and maintainable programs.