Creating Custom Modules

Any Python file is a module! Create your own modules to organize code into logical, reusable units.

15 min•By Priygop Team•Updated 2026

Custom Modules

# Imagine we have a file called 'helpers.py':
# ---- helpers.py ----
# def greet(name):
#     return f"Hello, {name}!"
# 
# def add(a, b):
#     return a + b
# 
# PI = 3.14159
# ---- end helpers.py ----

# Then in main.py:
# from helpers import greet, add, PI
# print(greet("Alice"))
# print(add(5, 3))

# Demo: simulating a module
class MathHelper:
    PI = 3.14159
    E = 2.71828
    
    @staticmethod
    def circle_area(r):
        return MathHelper.PI * r ** 2
    
    @staticmethod
    def factorial(n):
        if n <= 1: return 1
        return n * MathHelper.factorial(n - 1)

# Use it like a module
print(f"PI = {MathHelper.PI}")
print(f"Circle area (r=5): {MathHelper.circle_area(5):.2f}")
print(f"5! = {MathHelper.factorial(5)}")

# Module best practices
# 1. Keep modules focused (one purpose)
# 2. Use descriptive names (utils.py, database.py)
# 3. Add docstrings to explain the module
# 4. Keep imports at the top of the file

Tip

Keep modules focused - one module per responsibility. utils.py, validators.py, models.py is cleaner than one huge helpers.py.

Diagram

Loading diagram…

Module = file, Package = folder + __init__.py, Library = pip.

Common Mistake

Warning

Naming your file the same as a standard library module (e.g., random.py, json.py) shadows the built-in. Use unique names.

Quick Quiz

Practice Task

Note

(1) Create a helpers.py module. (2) Import functions from it. (3) Add a docstring to your module.

Topics in This Module

Custom Modules

# Imagine we have a file called 'helpers.py':
# ---- helpers.py ----
# def greet(name):
#     return f"Hello, {name}!"
# 
# def add(a, b):
#     return a + b
# 
# PI = 3.14159
# ---- end helpers.py ----

# Then in main.py:
# from helpers import greet, add, PI
# print(greet("Alice"))
# print(add(5, 3))

# Demo: simulating a module
class MathHelper:
    PI = 3.14159
    E = 2.71828
    
    @staticmethod
    def circle_area(r):
        return MathHelper.PI * r ** 2
    
    @staticmethod
    def factorial(n):
        if n <= 1: return 1
        return n * MathHelper.factorial(n - 1)

# Use it like a module
print(f"PI = {MathHelper.PI}")
print(f"Circle area (r=5): {MathHelper.circle_area(5):.2f}")
print(f"5! = {MathHelper.factorial(5)}")

# Module best practices
# 1. Keep modules focused (one purpose)
# 2. Use descriptive names (utils.py, database.py)
# 3. Add docstrings to explain the module
# 4. Keep imports at the top of the file

Topics in This Module