📃 Python Modules

Last Updated: 17th August 2025

  • A module is a .py file that contains functions, variables, or classes you can reuse.
  • Think of it like a toolbox: import it and use the tools inside.

Hinglish Tip 🗣: Module ko toolbox samjho. Ek baar tools bana liye, baar-baar use kar sakte ho—sirf import karo.

Module Types

There are Three Types of Modules:

  1. User-Defined Modules: Created by you.
  2. Built-in Modules: Part of the Python Standard Library.
  3. Third-Party Modules: External libraries.

User-Defined Modules

It help you organize your code into modules.

Folder layout (same directory):

project/
├─ myutils.py
└─ main.py

In myutils.py, we can write any functions, variables, or classes that we want to use in main.py.

# myutils.py
PI = 3.14159

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

def square(x):
    return x * x

# run-only-when-this-file-is-executed-directly
if __name__ == "__main__":
    print("Quick self-test:", add(2, 3), square(4))

Hinglish Tip 🗣: name == "main" ka matlab: yeh code sirf tab chalega jab file direct run ho—import hone par nahi.

In main.py:

# main.py
# 1) Import full module
import myutils            # import your module
print(myutils.add(10, 5))   # 15
print(myutils.square(6))    # 36

# 2) Import specific names
from myutils import add, square
print(add(10, 5))   # 15
print(square(6))    # 36

# 3) Import all names
from myutils import *
print(add(10, 5))   # 15
print(square(6))    # 36
print(PI)           # 3.14159

# 4) Import with alias (short name)
import myutils as utils
print(utils.add(10, 5))   # 15
print(utils.square(6))    # 36

# 5) Import with alias (short name) and specific names
from myutils import add as a, square as s
print(a(10, 5))   # 15
print(s(6))       # 36

Built-in Modules

It is part of the Python Standard Library, and you can use it without installing any additional packages.Some of them are: math, random, datetime,time,os,re,csv etc.

Third-Party Modules

Third-party modules are packages that are not part of the Python Standard Library. You can install them using the pip package manager.e.g. numpy, pandas, matplotlib etc.

Hinglish Tip 🗣: pip ka matlab: Python ka koi bhi library install karo, toh pip ka use karo.

💡 Quick Practice

  • Create a module calc.py with functions: add(a,b), mean(lst) (no external libs). Import in another file and test.
  • Make stringtools.py with to_snake(name: str) -> str and show usage from main.py.
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