🔹 What is a Python Module?

A module in Python is a file containing Python functions, classes, and variables that can be imported and reused in other programs.

• It helps organize code logically.
• Reduces redundancy and improves code reusability.
• A module is simply a Python file (.py) that can be imported into another script.

✅ Example of a module (mymodule.py):

# mymodule.py
def greet(name):
    return f"Hello, {name}!"

pi = 3.14159

✅ Using the module (main.py):

import mymodule

print(mymodule.greet("Alice"))  # Output: Hello, Alice!
print(mymodule.pi)  # Output: 3.14159

---

🔹 Types of Python Modules

Python modules are categorized into three types:
1️⃣ Built-in Modules (Pre-installed)
2️⃣ User-Defined Modules (Custom-created)
3️⃣ External Modules (Installed via pip)

---

1️⃣ Built-in Modules (Standard Library)

Python comes with many built-in modules that provide useful functions.

✅ Examples of Built-in Modules

Module	Purpose
math	Mathematical functions
random	Generate random numbers
os	Operating system interaction
sys	System-specific parameters and functions
time	Time-related functions
datetime	Work with dates and times
json	Work with JSON data
re	Regular expressions

🔹 Example 1: Using the math module

import math

print(math.sqrt(16))  # Output: 4.0
print(math.factorial(5))  # Output: 120

🔹 Example 2: Using the random module

import random

print(random.randint(1, 10))  # Output: Random number between 1 and 10
print(random.choice(['apple', 'banana', 'cherry']))  # Output: Random choice

---

2️⃣ User-Defined Modules

These are modules created by users to organize code efficiently.

✅ Creating a module (greetings.py)

# greetings.py
def say_hello(name):
    return f"Hello, {name}!"

def say_goodbye(name):
    return f"Goodbye, {name}!"

✅ Using the module (main.py)

import greetings

print(greetings.say_hello("Alice"))  # Output: Hello, Alice!
print(greetings.say_goodbye("Alice"))  # Output: Goodbye, Alice!

✅ Importing specific functions

from greetings import say_hello

print(say_hello("Bob"))  # Output: Hello, Bob!

---

3️⃣ External Modules (Third-Party)

These modules are not included in Python by default but can be installed using pip.

✅ Examples of External Modules

Module	Purpose
numpy	Numerical computing
pandas	Data analysis
requests	HTTP requests
flask	Web development
matplotlib	Data visualization
scipy	Scientific computing

✅ Installing an external module (requests)

pip install requests

✅ Using the installed module

import requests

response = requests.get("https://api.github.com")
print(response.status_code)  # Output: 200

---

🔹 Importing Modules in Python

Python provides several ways to import modules.

1️⃣ Importing the Entire Module

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

2️⃣ Importing a Specific Function

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

3️⃣ Importing with an Alias

import math as m
print(m.sqrt(25))  # Output: 5.0

4️⃣ Importing All Functions (Not Recommended)

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

⚠️ Caution: This can cause name conflicts if multiple modules have functions with the same name.

---

🔹 Finding Module Location

If you want to check where a module is installed:

import os
print(os.__file__)  # Outputs the path of the os module

---

🔹 Checking Available Functions in a Module

import math
print(dir(math))  # Lists all functions in the math module

---

🔹 Creating and Using a Package

A package is a collection of modules organized in folders.

✅ Folder structure:

my_package/
│── __init__.py
│── module1.py
│── module2.py

✅ module1.py

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

✅ Using the package

from my_package import module1

print(module1.greet("Alice"))  # Output: Hello, Alice!

---

🔹 Summary Table

Type of Module	Description	Example
Built-in Modules	Pre-installed with Python	math, random, os
User-Defined Modules	Custom-created modules	mymodule.py
External Modules	Installed via pip	numpy, pandas, requests

---

🎯 Final Thoughts

✅ Modules help in organizing and reusing code efficiently.
✅ Python has built-in, user-defined, and external modules.
✅ Using pip, we can install third-party modules.

Would you like me to explain modules in depth with real-world projects? 🚀