🐍MODULES AND PACKAGES IN PYTHON

Modules and packages help organize Python code into reusable, maintainable, and logical units.

1) What is a Module?

A module is a single Python file (.py) that contains Python code — functions, classes, or variables — that can be imported and reused in other Python programs.

# example_module.py
def greet(name):
    return f"Hello, {name}!"

pi = 3.14159

2) How to Use a Module

You can import modules using the import statement:

# main.py
import example_module

print(example_module.greet("Alice"))
print(example_module.pi)

Other ways to import:

# Import specific items
from example_module import greet, pi

# Import with alias
import example_module as em
print(em.greet("Bob"))

3) What is a Package?

A package is a collection of Python modules organized in directories with a special file __init__.py. Packages allow better organization of large projects.

project/
│
├── package_name/
│   ├── __init__.py
│   ├── module1.py
│   └── module2.py
└── main.py

4) How to Use a Package

# Import a module from a package
from package_name import module1

module1.some_function()

# Import specific item
from package_name.module2 import some_class

obj = some_class()

Packages can also have nested packages, making it easy to organize large projects.

5) Common Built-in Modules

Python comes with a rich standard library of modules:

• math – Mathematical operations
• os – Interact with the operating system
• sys – Python runtime environment
• random – Random numbers and selections
• datetime – Date and time operations
• json – Working with JSON data

import math
print(math.sqrt(16))  # 4.0

import random
print(random.choice([1, 2, 3, 4]))  # random element

6) Differences Between Modules and Packages

Aspect	Module	Package
Definition	Single Python file (.py)	Directory of modules containing __init__.py
Purpose	Organize reusable code in one file	Organize multiple modules and subpackages
Example	math.py	numpy/ (contains multiple modules)

7) Common Mistakes

• Importing modules/packages that don’t exist → ModuleNotFoundError
• Using relative imports incorrectly in packages
• Using the same name as a built-in module (e.g., naming your file math.py) → conflicts
• Forgetting __init__.py in older Python versions (needed for package recognition)

Next Steps

Next, we will explore Exceptions and Error Handling in Python to make your code more robust.

➡️ Next: File handling and OS interaction in Python

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