Python Modules

What is a Module?

A module in Python is a file that contains Python code (functions, classes, and variables) that you can reuse in other programs. Modules help you organize your code into logical sections and avoid repeating yourself.

There are two types of modules:
1. Built-in modules -- come with Python (e.g., os, io, math).
2. User-defined modules -- created by you in separate .py files.

You use the import statement to load a module into your program.

Importing a Module

import math

print(math.sqrt(16))  # 4.0
print(math.pi)        # 3.141592653589793

You can also import specific functions:

from math import sqrt, pi

print(sqrt(25))  # 5.0
print(pi)        # 3.141592653589793

Example 1: The `os` Module

The os module provides functions to interact with the operating system (files, directories, environment variables).

import os

# Check if a file exists
if os.path.exists("example.txt"):
    print("File already exists!")
else:
    print("File does not exist yet.")

This helps you safely check before creating, reading, or writing files.

Example 2: The `io` Module

The io module provides tools for handling input and output (working with files in text and binary modes).

import io

# Write text to a file
f = io.open("example_io.txt", "w", encoding="utf-8")
f.write("Hello, this is written using the io module.")
f.close()

# Read the text back
f = io.open("example_io.txt", "r", encoding="utf-8")
content = f.read()
print(content)  # "Hello, this is written using the io module."
f.close()

Why Use Modules?

Organization → Keeps code clean and modular.
Reusability → Functions can be used in multiple programs.
Built-in Power → Python modules provide ready-to-use functionality.

More Resources

Summary

Modules are reusable pieces of Python code.
Use import to load built-in or custom modules.
os is used for file and system operations (like checking if a file exists).
io is used for reading and writing to files.

Modules not only help with organization but also enable reusability—you can write code once and use it across many projects.