Introduction to Python Modules

Python modules are reusable pieces of code that simplify programming by providing pre-defined functionalities. A module can contain functions, classes, and variables that you can import into your program to extend its capabilities.

What Are Modules?

A module in Python is simply a file with the .py extension that contains Python code. You can:

• Use built-in modules provided by Python.
• Create your custom modules for specific tasks.
• Install third-party modules using pip.

Why Use Modules?

Modules offer the following benefits:

1. Code Reusability

   • Write a function once and use it across multiple projects by importing the module.

2. Saves Time

   • Instead of writing code from scratch, use pre-built modules to achieve your goal faster.

3. Better Code Organization

   • Split large programs into smaller, logical pieces using modules.

4. Enhanced Functionality

   • Access advanced features like web scraping, data analysis, or GUI development using third-party modules.

Importing Modules

You can import a module in various ways:

1. Basic Import

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

2. Import Specific Functions

   from math import sqrt
   print(sqrt(25))  # Output: 5.0

3. Alias Modules

   import pandas as pd
   df = pd.DataFrame({"Name": ["Rhea", "Nitya"], "Age": [25, 30]})
   print(df)

4. Import All Functions (Not Recommended)

   from math import *
   print(sin(90))

Types of Modules

1. Built-In Modules

   • Already included in Python and require no installation.
   • Examples: os, sys, math, random.

2. Third-Party Modules

   • Developed by the Python community and installed via pip.
   • Examples: numpy, requests, matplotlib.

3. Custom Modules

   • Created by users to organize their reusable code.

Popular Python Modules and Their Utilities

How to Install Third-Party Modules?

You can install third-party modules using pip, the Python package manager.
For example, to install the requests module, run the following command in your terminal:

pip install requests

Example:

import requests
 
response = requests.get("https://www.pythonforall.com")
print(response.status_code)

Creating Your Own Module

You can create a module by saving a Python file with functions, classes, or variables.

Example: Creating a Custom Module

File: greetings.py

def say_hello(name):
    print(f"Hello, {name}! Welcome to PythonForAll.")

File: main.py

import greetings
 
greetings.say_hello("Rhea")
# Output: Hello, Rhea! Welcome to PythonForAll.

Best Practices for Using Modules

1. Use Built-In Modules First

   • Always check if Python provides a built-in module before installing third-party ones.

2. Follow Naming Conventions

   • Use descriptive names for custom modules.

3. Avoid Name Conflicts

   • Ensure your custom module names don’t clash with built-in or popular third-party modules.

4. Keep Code Organized

   • Store your modules in separate files or folders for better project structure.

Try It Yourself

Problem 1: Import and Use the math Module

Write a program to calculate the area of a circle given its radius using the math module.

import math
 
radius = float(input("Enter the radius of the circle: "))
area = math.pi * math.pow(radius, 2)
print("Area of the circle:", area)

Problem 2: Create and Use a Custom Module

Write a custom module calculator.py that contains functions for addition and multiplication. Import and use it in another script.

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

import calculator
 
print("Sum:", calculator.add(5, 3))        # Output: Sum: 8
print("Product:", calculator.multiply(5, 3))  # Output: Product: 15