Creating Custom Modules

A custom module is a Python file (.py) that contains functions, variables, or classes which can be reused in other programs.

Creating your own modules helps you:

• Organize large programs
• Reuse code easily
• Improve readability
• Build professional projects

STEP 1: CREATE A MODULE FILE

Create a new Python file, for example:

my_module.py

def greet(name):
    return "Hello " + namedef add(a, b):
    return a + b

This file is now a custom module.

STEP 2: IMPORT THE MODULE

In another Python file (for example main.py):

import my_moduleprint(my_module.greet("Hira"))
print(my_module.add(5, 3))

Both files must be in the same folder.

IMPORT SPECIFIC FUNCTIONS

from my_module import greetprint(greet("Ali"))

Now you don’t need to write my_module.greet().

USING ALIAS

import my_module as mmprint(mm.add(10, 20))

Alias makes long names shorter.

ADDING VARIABLES IN MODULE

You can also define variables inside a module.

my_module.py

pi_value = 3.14

Use it like this:

import my_moduleprint(my_module.pi_value)

USING MAIN CHECK (BEST PRACTICE)

To prevent code from running automatically when imported:

def greet():
    print("Hello!")if __name__ == "__main__":
    greet()

This ensures the function runs only when the file is executed directly.

MODULE SEARCH PATH

Python looks for modules:

• In the current folder
• In system library folders
• In installed packages

You can check path using:

import sys
print(sys.path)

BENEFITS OF CUSTOM MODULES

• Code reusability
• Better structure
• Easier maintenance
• Professional project organization

KEY TAKEAWAYS

• A module is simply a .py file
• Use import module_name to use it
• Keep modules in the same directory
• Use if __name__ == "__main__" for best practice

Creating custom modules is an important step toward building large and well-structured Python applications.