⭐ Python Packages

A package in Python is a way of organizing related modules into a directory (folder) structure.
Packages make it easier to structure large programs and avoid name conflicts.

👉 Package = A folder containing multiple Python modules + an __init__.py file

In simple words:

Module = A single Python file (.py)
Package = A folder containing modules

⭐ Why Do We Need Packages?

✔ To group related modules
✔ For better code organization
✔ To avoid naming conflicts
✔ To support large-scale project development
✔ To reuse code across multiple projects
✔ To make distribution easier

⭐ Structure of a Package

A typical package structure looks like this:

myproject/
    mathpkg/
        __init__.py
        addition.py
        subtraction.py
        multiply.py
    main.py

📌 What is `init.py`?

Special file that identifies the folder as a Python package
Can be empty
May contain initialization code
Runs when the package is imported

Before Python 3.3, it was mandatory; now it is optional but still recommended.

⭐ Creating a Python Package (Step-by-Step)

✔ Step 1: Create a Folder (Package)

Create a folder named myutils

myutils/

✔ Step 2: Add `init.py` file

myutils/
    __init__.py   # can be empty

✔ Step 3: Add Modules Inside the Package

Example modules:

addition.py

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

subtraction.py

def sub(a, b):
    return a - b

✔ Step 4: Use the Package in Another Program

from myutils.addition import add
from myutils.subtraction import sub

print(add(10, 20))
print(sub(50, 15))

⭐ Importing Packages

There are many ways to import from packages:

1. Import Entire Package

import myutils

2. Import Module from Package

import myutils.addition

3. Import Function Directly

from myutils.addition import add

4. Import All Modules

from myutils import *

(works only if __init__.py contains __all__ list)

Example:

__all__ = ["addition", "subtraction"]

⭐ Built-in Python Packages

Many Python libraries come packaged:

Package	Description
`os`	Operating system interface
`sys`	System parameters
`json`	JSON handling
`numpy`	Scientific computing
`pandas`	Data analysis
`matplotlib`	Plotting
`tkinter`	GUI toolkit
`collections`	Specialized data structures

⭐ Installing Third-Party Packages

Use pip, Python’s package manager:

pip install numpy
pip install pandas

To uninstall:

pip uninstall numpy

To list installed packages:

pip list

⭐ Difference Between Module and Package (Exam Point)

Module	Package
Single `.py` file	Folder containing modules
Small code unit	Large code grouping
No directory required	Requires directory structure
Cannot contain submodules	Can contain submodules and subpackages
Example: `math.py`	Example: `numpy` package

⭐ Advantages of Packages

✔ Organizes large projects
✔ Avoids name conflicts
✔ Promotes code reusability
✔ Supports modular programming
✔ Allows distribution of libraries
✔ Makes maintenance easier

⭐ Exam-Ready Short Answer

A Python package is a collection of related modules organized in a directory containing an __init__.py file. Packages help structure large programs, avoid naming conflicts, and promote code reusability. Example: NumPy, Pandas, Matplotlib, Requests.

Python Packages