Python Modules

Python Modules Overview

Modules in Python are files containing Python code that can define functions, classes, and variables. They allow for code organization and reusability, enabling you to break your program into manageable pieces. Here’s a guide to understanding and using Python modules effectively.

1. Creating a Module: A module is simply a Python file with a .py extension. You can create a module by defining functions, classes, or variables in it.

   # my_module.py
   def greet(name):
       return f"Hello, {name}!"
   
   pi = 3.14159

2. Importing a Module: You can import a module into another Python script using the import statement.

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

3. Importing Specific Items: If you only need specific functions or variables from a module, you can import them directly.

   from my_module import greet, pi
   
   print(greet("Bob"))  # Output: Hello, Bob!
   print(pi)            # Output: 3.14159

4. Renaming Imported Modules: You can rename modules or functions upon import to avoid naming conflicts or for convenience.

   import my_module as mm
   
   print(mm.greet("Charlie"))  # Output: Hello, Charlie!

5. Using __name__: Each module has a special built-in attribute called __name__. When a module is run directly, __name__ is set to "__main__". This allows you to write code that runs only when the module is executed directly, and not when imported.

   # my_module.py
   def greet(name):
       return f"Hello, {name}!"
   
   if __name__ == "__main__":
       print(greet("Main Module"))

6. Built-in Modules: Python comes with a variety of built-in modules, which you can import and use directly. Examples include math, os, sys, and datetime.

   import math
   
   print(math.sqrt(16))  # Output: 4.0
   print(math.pi)        # Output: 3.141592653589793

7. Creating a Package: A package is a collection of modules organized in a directory. To create a package, simply create a directory and include an __init__.py file (can be empty) to mark it as a package.

   my_package/
       __init__.py
       module1.py
       module2.py

8. Importing from Packages: You can import modules from packages just like regular modules, using dot notation.

   from my_package import module1
   
   module1.some_function()

9. Third-Party Modules: You can also use third-party modules that can be installed using pip. For example, to install requests, you can use:

   pip install requests

   After installation, you can import and use it in your code.

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

Python Modules Example

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

pi = 3.14159

# main.py
import my_module

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

# Importing specific items
from my_module import greet, pi

print(greet("Bob"))  # Output: Hello, Bob!
print(pi)            # Output: 3.14159

# Renaming imported module
import my_module as mm

print(mm.greet("Charlie"))  # Output: Hello, Charlie!

# Using built-in module
import math

print(math.sqrt(16))  # Output: 4.0
print(math.pi)        # Output: 3.141592653589793

# Creating a package
# Directory structure:
# my_package/
#     __init__.py
#     module1.py
#     module2.py

# Importing from package
from my_package import module1

module1.some_function()

# Using third-party module
import requests

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