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4.3 MODULE, PACKAGE AND LIBRARY IN PYTHON

Introduction

Python provides reusable code using modules, packages, and libraries. These help programmers write organized, reusable, and efficient programs.

 

Easy Memory Trick

Term	Meaning	Example
Module	Single Python file	math.py
Package	Folder containing modules	numpy.random
Library	Collection of packages and modules	NumPy, Pandas

 

Easy Analogy

Library = House
Package = Room
Module = Book

A house contains rooms, and rooms contain books.

Similarly:

Library → Packages → Modules

 

MODULE

Definition

A module is a single Python file (.py) containing reusable code such as functions, classes, variables, and statements.

Modules help reduce repetition and make programs organized.

 

Types of Modules

 

1. Built-in Module

A built-in module is a module already provided by Python that contains predefined functions, classes, and variables to perform specific tasks.

These modules are available automatically after Python installation.

 

Examples

·         math

·         random

·         os

·         sys

·         datetime

 

Example Program

import math

print(math.sqrt(25))

 

Output

5.0

 

2. User-defined Module

A user-defined module is a module created by the programmer to store reusable code such as functions, classes, and variables in a separate Python file.

Example

# calculator.py

def add(a, b):

    return a + b

Using the Module

import calculator

print(calculator.add(5, 3))

 

Output

8

 

Advantages of Modules

1.      Reuse code multiple times

2.      Reduce code duplication

3.      Make programs organized

4.      Simplify testing and debugging

5.      Improve readability

 

Methods of Importing Modules

 

1. Import Entire Module

import math

Example

print(math.factorial(5))

Output

120

 

2. Import Specific Function

from math import sqrt

Example

print(sqrt(49))

Output

7.0

 

3. Import Module Using Alias

An alias is an alternative short name given to a module during import using the as keyword.

Example

import math as m

print(m.sqrt(64))

Output

8.0

 

4. Import all functions from a module

Importing all functions from a module means importing every function, variable, and object from a module into the current program using the * symbol.

 

from module_name import *

 

Example:

 

from math import *

 

print(sqrt(25))

print(factorial(5))

 

Output

5.0

120

 

Important Point

After importing with *, functions can be used directly without writing the module name.

Example:

sqrt(25)

Instead of:

math.sqrt(25)

 

PACKAGE

Definition

A package is a collection of related Python modules organized inside a folder or directory.

Packages help organize large Python projects systematically.

 

Structure of a Package

calculator/

│

├── add.py

├── subtract.py

└── __init__.py

 

init.py File

__init__.py is a special file used to indicate that a directory should be treated as a Python package.

 

Advantages of Packages

1.      Groups related modules together

2.      Organizes large projects

3.      Improves code management

4.      Avoids naming conflicts

5.      Supports hierarchical structure

 

Example of Package Import

from calculator.add import add

 

Important Points About Packages

·         Contains one or more modules

·         Usually includes __init__.py

·         Can contain sub-packages

·         Provides hierarchical organization

 

 

 

LIBRARY

Definition

A library is a collection of modules and packages that provides reusable functionality for specific tasks.

Libraries help programmers perform complex tasks easily and quickly.

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Types of Libraries

1. Standard Library

A standard library is a collection of built-in modules that are automatically available with Python installation.

Examples

·         math

·         random

·         os

·         datetime

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2. External Library

An external library is a library that is not included with Python by default and must be installed separately using pip.

Examples

·         NumPy

·         Pandas

·         Matplotlib

·         TensorFlow

·         OpenCV

·         Django

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Popular Python Libraries

Library	Main Use
NumPy	Numerical Computing
Pandas	Data Analysis
Matplotlib	Data Visualization
Requests	API Calls
TensorFlow	Machine Learning
OpenCV	Computer Vision
Django	Web Development

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pip

Definition

pip is Python’s package manager used to install, update, and remove external packages and libraries.

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Common pip Commands

Install Package

pip install numpy

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Uninstall Package

pip uninstall numpy

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Show Installed Packages

pip list

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Check pip Version

pip --version

Advantages of pip

1.      Installs external libraries easily

2.      Updates packages

3.      Removes unwanted packages

4.      Manages dependencies

5.      Simplifies package management

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📊 Difference Between Module, Package and Library

Feature	Module	Package	Library
Meaning	Single Python file	Collection of modules	Collection of packages and modules
Size	Smallest	Medium	Largest
Form	.py file	Folder/Directory	Complete collection
Purpose	Reuse code	Organize modules	Provide complete functionality
Example	math.py	numpy.random	NumPy

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Common Exam Mistakes

❌ Confusing module and package
❌ Writing package as a single file
❌ Forgetting .py extension in module definition
❌ Writing pip as a library instead of package manager

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Final Summary

A module is a single Python file containing reusable code. A package is a collection of related modules stored inside a folder. A library is a collection of modules and packages that provides reusable functionality for developers.