What is a module in Python?

A module is a file containing definitions and instructions in Python. It allows organizing code, making it more structured, reusable, and understandable. Modules have the extension .py.

Main advantages of using modules:

• Code organization: Breaking a large program into smaller, manageable files.
• Reusability: The ability to import and use functions, classes, and variables defined in another module.
• Name isolation: Each module has its own namespace, preventing name conflicts.

Modules are imported using the import keyword.

# Importing an entire module
import math

# Using a function from the imported module
print(math.sqrt(16))

You can import specific objects from a module:

# Importing a specific function
from math import sqrt

# Using the imported function directly
print(sqrt(25))

There are different types of modules:

1. Built-in modules: Part of Python's standard library (e.g., math, os, sys).
2. User-defined modules: Created by developers for specific projects.
3. Third-party modules: Installed via package managers (e.g., pip) (e.g., requests, django).

A module's namespace is accessible via <module_name>.<object_name>.

import math

# Accessing a constant from the math module
print(math.pi)

When a module is imported, Python executes its code. If the module is imported again within the same session, its code is not executed again; the already loaded object is used.

# my_module.py
print("My_module loaded")

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

# main.py
import my_module # Will print "My_module loaded"

my_module.greet("World")

import my_module # Will not print anything, as the module is already loaded

A module can be reloaded using the reload function from the importlib module (Python 3+).

# importlib.reload(module_name)