Introduction to Python Modules

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A module in Python is a file that contains Python code, typically including functions, classes, and variables. Modules help organize and reuse code efficiently.

1. What is a Python Module?

A module is simply a .py file containing reusable code. Python provides built-in modules, and you can also create custom modules.

Example of a Simple Module:

Create a file mymodule.py with the following code:

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

Now, import and use it in another Python file:

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

2. Importing Modules

Python provides multiple ways to import modules:

  • import module_name – Imports the whole module.
  • from module_name import function_name – Imports specific functions or variables.
  • import module_name as alias – Imports with an alias.
  • from module_name import * – Imports everything (not recommended).

Example:

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

from math import pi
print(pi)  # Output: 3.141592653589793

import math as m
print(m.factorial(5))  # Output: 120

3. Built-in Python Modules

Python has many built-in modules, such as:

  • math – Mathematical functions
  • random – Generating random numbers
  • datetime – Handling dates and times
  • os – Interacting with the operating system
  • sys – System-specific parameters and functions

Example of Using random Module:

import random
print(random.randint(1, 10))  # Generate a random number between 1 and 10

4. Creating and Using Custom Modules

You can create your own module by saving Python functions in a .py file and importing them.

Example:

Create calculator.py with:

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

Now, use it in another file:

import calculator
print(calculator.add(5, 3))  # Output: 8

5. The __name__ Variable in Modules

When a Python script runs, the __name__ variable determines if the script is being run directly or imported.

Example:

if __name__ == "__main__":
    print("This script is run directly!")
else:
    print("This script is imported as a module.")

6. The dir() Function

The dir() function lists all attributes and methods of a module.

Example:

import math
print(dir(math))

7. Installing External Modules using pip

Python allows installing third-party modules using pip, the package manager.

Example:

pip install requests

Now, use the installed module:

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

8. Summary

✅ Modules help organize and reuse Python code efficiently.
✅ Built-in modules like math, random, and os simplify complex tasks.
✅ Custom modules allow the creation of reusable functions.
✅ The __name__ variable differentiates between script execution and module import.
✅ External modules can be installed via pip.

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