Modules and Packages in Python

Understanding Python modules and packages: how to organize code, import functionality, create reusable files, and structure large applications.

What is a Module?

In Python, every .py file is a module. Modules help organize code into separate files and allow reuse across projects.

1. Creating and Importing a Module

Creating your own module and importing it.

Different Import Styles

Import statements allow flexibility in how we access module contents.

1. Import Specific Functions

Import only what you need.

2. Import with Alias

Using shorter names.

Built-in Modules

The Python Standard Library provides powerful modules ready to use.

1. Using Built-in math Module

Example using math module.

__name__ Special Variable

Every Python module has a special variable called __name__. It tells whether the file is run directly or imported.

1. Using if __name__ == "__main__"

Prevent code from running on import.

What is a Package?

Packages help organize multiple related modules inside directories.

1. Basic Package Structure

Folder-based organization.

Importing from Packages

You can import modules or functions from inside a package.

1. Import Example

Importing from package.

Importing from Parent or Multiple-Level Folders

Unlike JavaScript, Python does not directly support relative path imports like "../.." in scripts. Instead, Python uses package-based imports and the module search path (sys.path). There are three proper ways to handle multi-level imports.

1. Proper Project Structure (Recommended)

Use packages instead of path hacks.

2. Absolute Import (Best Practice)

Import using full package path.

3. Relative Imports (Inside Packages Only)

Using dot notation for current, parent, and multiple parent folders.

4. Modifying sys.path (Not Recommended for Production)

Manual multi-level folder import.

5. Best Practice Summary

How professionals handle multi-level imports.

Installing Third-Party Packages

Most real-world Python applications rely on external libraries. These libraries are hosted on PyPI (Python Package Index). Python uses pip as its official package manager to install and manage them. In this section, we will learn how to properly work with third-party packages in a safe and professional way.

1. Installing a Package

Install a library from PyPI using pip.

2. Using requirements.txt

Save and reinstall project dependencies easily.

3. Deleting (Uninstalling) a Package

Remove an installed package from your environment.

4. Upgrading a Package

Update a package to the latest available version.

5. Virtual Environments (Highly Recommended)

Isolate dependencies for each project.

6. Best Practices

Professional recommendations for managing third-party packages.