MODULE 6: Python Modules & Packages

Python allows you to organize large programs into reusable, manageable components using modules and packages.

1. What are Modules?

Brief

A module is a Python file (.py) that contains variables, functions, and classes which can be reused in other programs.

Why Modules Are Important

• Improves code reusability
• Makes code more organized
• Easier debugging and maintenance
• Enables teamwork in large projects

Example

# math_operations.py (module)
def add(a, b):
    return a + b

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

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2. Importing Modules

Brief

Importing allows you to use code written in another module.

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Ways to Import Modules

1. import module_name

import math
print(math.sqrt(16))

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2. import module as alias

import math as m
print(m.pi)

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3. from module import function

from math import sqrt
print(sqrt(25))

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**4. from module import ***

(Not recommended – pollutes namespace)

from math import *
print(pi)

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3. Built-in Modules

Brief

Python provides many ready-to-use built-in modules.

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Common Built-in Modules & Usage

math

import math
print(math.factorial(5))
print(math.ceil(4.3))

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random

import random
print(random.randint(1, 10))

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datetime

from datetime import datetime
print(datetime.now())

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os

import os
print(os.getcwd())

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sys

import sys
print(sys.version)

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4. Creating Custom Modules

Brief

You can create your own module by simply creating a .py file.

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Step 1: Create Module

# calculator.py
def multiply(a, b):
    return a * b

def divide(a, b):
    return a / b

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Step 2: Use Module

import calculator

print(calculator.multiply(5, 4))

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Using Alias

import calculator as calc
print(calc.divide(10, 2))

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5. Python Packages

Brief

A package is a collection of related modules organized in folders.

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Package Structure

mypackage/
│
├── __init__.py
├── math_utils.py
├── string_utils.py

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Example Module

# math_utils.py
def square(n):
    return n * n

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Import from Package

from mypackage.math_utils import square
print(square(6))

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Why Packages Are Used

• Organize large applications
• Avoid name conflicts
• Improve scalability

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6. pip & Virtual Environments

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6.1 pip (Python Package Installer)

Brief

pip is used to install third-party libraries from PyPI.

Common Commands

pip install numpy
pip install pandas
pip uninstall numpy
pip list

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6.2 Virtual Environments

Brief

A virtual environment creates an isolated Python environment for each project.

Why Virtual Environments Matter

• Prevent dependency conflicts
• Maintain clean project setup
• Used in real-world deployments

Create Virtual Environment

python -m venv venv

Activate Virtual Environment

Windows

venv\Scripts\activate

Mac/Linux

source venv/bin/activate

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7. requirements.txt

Brief

requirements.txt lists all project dependencies.

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Generate requirements.txt

pip freeze > requirements.txt

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Sample requirements.txt

numpy==1.26.2
pandas==2.1.0
flask==3.0.0

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Install from requirements.txt

pip install -r requirements.txt