setting-up-python-libraries

Python Library Project Setup

Quick Start

Create a new library with this structure:

my-library/
├── src/my_library/
│   ├── __init__.py
│   └── py.typed
├── tests/
├── pyproject.toml
├── Makefile
├── .pre-commit-config.yaml
└── .github/workflows/ci.yml

Use src/ layout to prevent accidental imports of development code.

Core Configuration

For complete templates, see:

• PYPROJECT.md - Full pyproject.toml with all tool configs
• CI.md - GitHub Actions and pre-commit setup
• MAKEFILE.md - Makefile automation patterns

Minimal pyproject.toml

[build-system]
requires = ["setuptools>=61.0", "wheel"]
build-backend = "setuptools.build_meta"

[project]
name = "my-library"
version = "0.1.0"
description = "What it does"
readme = "README.md"
requires-python = ">=3.10"
license = {text = "MIT"}
dependencies = []

[project.optional-dependencies]
dev = ["pytest>=7.0", "ruff>=0.1", "mypy>=1.0"]

[tool.setuptools.packages.find]
where = ["src"]

Essential Commands

# Setup
pip install -e ".[dev]"
pre-commit install

# Daily workflow
ruff check src tests        # Lint
ruff format src tests       # Format
pytest                      # Test
mypy src                    # Type check

Key Decisions

Choice	Recommendation	Why
Layout	src/	Catches packaging bugs early
Build backend	setuptools	Mature, broad compatibility
Linter	ruff	Fast, replaces flake8+isort+black
Python range	>=3.10	Don't pin exact versions
Dependencies	Minimal	Move optional deps to extras

Checklist

Project Setup:
- [ ] src/ layout with py.typed marker
- [ ] pyproject.toml (not setup.py)
- [ ] Makefile with dev/test/lint/format
- [ ] .pre-commit-config.yaml
- [ ] .github/workflows/ci.yml
- [ ] README.md, LICENSE, CHANGELOG.md
- [ ] .gitignore

Helper Script

Create a new project structure:

python scripts/create_project.py my-library --author "Name"

Learn More

This skill is based on the Guide to Developing High-Quality Python Libraries by Will McGinnis. See these posts for deeper coverage:

• Defining Library Scope
• Dependency Management
• Licensing Your Project
• pyproject.toml Explained