Modules & Packages in Python

Learn how Python modules and packages help us organize and reuse code in different programs.

What is a Module?

A module is simply a Python file that contains Python code such as variables, functions and classes.

A module usually has the .py extension.

Instead of writing the same code again and again, we can place reusable code inside a module and use it in another Python program.

Example 📩🌍

Suppose we have a training institute application. We may keep student-related functions in one file, fee-related functions in another file and utility functions in another file.

What is a Package?

A package is a collection of related Python modules organized inside a directory.

Packages help us organize larger applications into meaningful sections.

Module and Package Diagram

The following diagram shows the basic relationship between modules and packages.

Creating a Simple Module

First, create a file named: calculator.py

def add(a, b):

    return a + b


def subtract(a, b):

    return a - b

Here, calculator.py is a module containing two reusable functions.

Using a Module

Now create another file named: main.py

import calculator

print(calculator.add(10, 20))
print(calculator.subtract(20, 5))

Output:

30
15

The calculator module is imported into main.py and its functions are reused.

Why Do We Use Modules?

• Reuse existing code.
• Avoid writing duplicate code.
• Keep programs organized.
• Make large programs easier to manage.
• Separate related functionality.

Basic Package Structure

A simple package structure can look like this:

myproject/
|
|-- main.py
|
|-- utilities/
|   |
|   |-- __init__.py
|   |
|   |-- calculator.py
|   |
|   |-- message.py

Here:

• myproject is the project folder.
• utilities is the package.
• calculator.py and message.py are modules.
• __init__.py is traditionally used to mark and initialize the package.

Module vs Package

Types of Python Modules

Importing a Module

Python provides the import statement to use a module.

import math

print(math.sqrt(25))

Output:

5.0

We will learn different import styles in detail in the next topic: Import Statement.

Benefits of Packages

• Organize large projects.
• Group related modules.
• Improve code maintainability.
• Make reusable components easier to manage.
• Help structure applications into logical sections.

Learning Flow

Practice Programs

1. Create a calculator.py module containing addition and subtraction functions.
2. Import the module into another Python file.
3. Create a small package containing two modules.
4. Use a built-in Python module such as math.
5. Explore the structure of a Python package.