Lesson 13: Modules and Packages in Python

🎯 Lesson Objective

To learn how to use and organize code with modules and packages, making programs modular, reusable, and easier to maintain.

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🧩 1. What Is a Module?

A module is a Python file (.py) containing functions, variables, and classes that can be imported into other programs.

✅ Example: Using the math module

import math

print(math.sqrt(16))   # Square root
print(math.factorial(5))  # Factorial

Output:

4.0
120

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⚙️ 2. Creating Your Own Module

1. Create a file mymodule.py:

def greet(name):
    print(f"Hello, {name}!")

pi = 3.14159

2. Use it in another program:

import mymodule

mymodule.greet("Sameer")
print("Value of pi:", mymodule.pi)

Output:

Hello, Sameer!
Value of pi: 3.14159

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🔄 3. Importing Specific Functions

from math import sqrt, factorial

print(sqrt(25))
print(factorial(4))

✅ Output:

5.0
24

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🧰 4. Using Aliases

import math as m

print(m.sqrt(36))
print(m.factorial(6))

Output:

6.0
720

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🧱 5. What Is a Package?

A package is a collection of Python modules organized in directories with an __init__.py file.
It helps structure large projects into multiple modules.

Example Structure:

my_package/
    __init__.py
    module1.py
    module2.py

Using a module from a package:

from my_package import module1
module1.function_name()

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🔄 6. Standard Library Modules

Python comes with many built-in modules:

Module	Description
os	Operating system interaction
sys	System-specific parameters
math	Mathematical functions
random	Random number generation
datetime	Date and time handling
json	JSON data handling
csv	CSV file operations

✅ Example: Random number

import random
print(random.randint(1, 100))  # Random integer between 1 and 100

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🛠️ 7. Installing External Modules

Use pip to install external modules:

pip install requests

✅ Example: Using requests module

import requests

response = requests.get("https://api.github.com")
print(response.status_code)

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🌍 8. Real-Life Example – Organizing Code

Create a package calculator:

calculator/
    __init__.py
    operations.py

operations.py:

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

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

Use in another file:

from calculator import operations

print(operations.add(10, 5))
print(operations.subtract(10, 5))

Output:

15
5