Lesson 20: Building and Packaging a Small Python Project

Why Packaging Matters

Packaging allows you to share your Python code with others, install it on different systems, or publish it to PyPI. A well‑structured project is easier to maintain, test, and extend.

Project Structure

A typical Python project layout looks like this:

myproject/
    myproject/
        __init__.py
        core.py
    tests/
        test_core.py
    README.md
    pyproject.toml
    LICENSE

Creating the Package Code

# myproject/core.py

def greet(name):
    return f"Hello, {name}!"

Adding __init__.py

This file marks the folder as a Python package:

# myproject/__init__.py

from .core import greet

Using pyproject.toml

This file defines metadata and build settings for your package:

[project]
name = "myproject"
version = "0.1.0"
description = "A simple example project"
authors = [{name = "Your Name"}]

[build-system]
requires = ["setuptools"]
build-backend = "setuptools.build_meta"

Adding a README

A README.md explains what your project does and how to use it.

Building the Package

Use the build tool:

pip install build
python -m build

This creates:

• .whl — wheel file (installable package)
• .tar.gz — source archive

Installing Your Package Locally

pip install dist/myproject-0.1.0-py3-none-any.whl

Publishing to PyPI

Upload using twine:

pip install twine
twine upload dist/*

Versioning Your Project

Follow semantic versioning:

• MAJOR — breaking changes
• MINOR — new features
• PATCH — bug fixes

Why Packaging Matters

• Makes your code reusable and shareable.
• Encourages clean project structure.
• Allows publishing to PyPI for others to install.
• Supports automated testing and CI workflows.

Next Steps

Now that you can build and package a Python project, you're ready to explore how to distribute applications in Lesson 21: Creating Executable Applications.

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