Source: wshobson/agents Original Plugin: python-development
Python Packaging
Comprehensive guide to creating, structuring, and distributing Python packages using modern packaging tools, pyproject.toml, and publishing to PyPI.
When to Use This Skill
- Creating Python libraries for distribution
- Building command-line tools with entry points
- Publishing packages to PyPI or private repositories
- Setting up Python project structure
- Creating installable packages with dependencies
- Building wheels and source distributions
- Versioning and releasing Python packages
- Creating namespace packages
- Implementing package metadata and classifiers
Core Concepts
1. Package Structure
- Source layout: src/package_name/(recommended)
- Flat layout: package_name/(simpler but less flexible)
- Package metadata: pyproject.toml, setup.py, or setup.cfg
- Distribution formats: wheel (.whl) and source distribution (.tar.gz)
2. Modern Packaging Standards
- PEP 517/518: Build system requirements
- PEP 621: Metadata in pyproject.toml
- PEP 660: Editable installs
- pyproject.toml: Single source of configuration
3. Build Backends
- setuptools: Traditional, widely used
- hatchling: Modern, opinionated
- flit: Lightweight, for pure Python
- poetry: Dependency management + packaging
4. Distribution
- PyPI: Python Package Index (public)
- TestPyPI: Testing before production
- Private repositories: JFrog, AWS CodeArtifact, etc.
Quick Start
Minimal Package Structure
my-package/
├── pyproject.toml
├── README.md
├── LICENSE
├── src/
│   └── my_package/
│       ├── __init__.py
│       └── module.py
└── tests/
    └── test_module.py
Minimal pyproject.toml
[build-system]
requires = ["setuptools>=61.0"]
build-backend = "setuptools.build_meta"
[project]
name = "my-package"
version = "0.1.0"
description = "A short description"
authors = [{name = "Your Name", email = "you@example.com"}]
readme = "README.md"
requires-python = ">=3.8"
dependencies = [
    "requests>=2.28.0",
]
[project.optional-dependencies]
dev = [
    "pytest>=7.0",
    "black>=22.0",
]
Package Structure Patterns
Pattern 1: Source Layout (Recommended)
my-package/
├── pyproject.toml
├── README.md
├── LICENSE
├── .gitignore
├── src/
│   └── my_package/
│       ├── __init__.py
│       ├── core.py
│       ├── utils.py
│       └── py.typed          # For type hints
├── tests/
│   ├── __init__.py
│   ├── test_core.py
│   └── test_utils.py
└── docs/
    └── index.md
Advantages:
- Prevents accidentally importing from source
- Cleaner test imports
- Better isolation
pyproject.toml for source layout:
[tool.setuptools.packages.find]
where = ["src"]
Pattern 2: Flat Layout
my-package/
├── pyproject.toml
├── README.md
├── my_package/
│   ├── __init__.py
│   └── module.py
└── tests/
    └── test_module.py
Simpler but:
- Can import package without installing
- Less professional for libraries
Pattern 3: Multi-Package Project
project/
├── pyproject.toml
├── packages/
│   ├── package-a/
│   │   └── src/
│   │       └── package_a/
│   └── package-b/
│       └── src/
│           └── package_b/
└── tests/
Complete pyproject.toml Examples
Pattern 4: Full-Featured pyproject.toml
[build-system]
requires = ["setuptools>=61.0", "wheel"]
build-backend = "setuptools.build_meta"
[project]
name = "my-awesome-package"
version = "1.0.0"
description = "An awesome Python package"
readme = "README.md"
requires-python = ">=3.8"
license = {text = "MIT"}
authors = [
    {name = "Your Name", email = "you@example.com"},
]
maintainers = [
    {name = "Maintainer Name", email = "maintainer@example.com"},
]
keywords = ["example", "package", "awesome"]
classifiers = [
    "Development Status :: 4 - Beta",
    "Intended Audience :: Developers",
    "License :: OSI Approved :: MIT License",
    "Programming Language :: Python :: 3",
    "Programming Language :: Python :: 3.8",
    "Programming Language :: Python :: 3.9",
    "Programming Language :: Python :: 3.10",
    "Programming Language :: Python :: 3.11",
    "Programming Language :: Python :: 3.12",
]
dependencies = [
    "requests>=2.28.0,<3.0.0",
    "click>=8.0.0",
    "pydantic>=2.0.0",
]
[project.optional-dependencies]
dev = [
    "pytest>=7.0.0",
    "pytest-cov>=4.0.0",
    "black>=23.0.0",
    "ruff>=0.1.0",
    "mypy>=1.0.0",
]
docs = [
    "sphinx>=5.0.0",
    "sphinx-rtd-theme>=1.0.0",
]
all = [
    "my-awesome-package[dev,docs]",
]
[project.urls]
Homepage = "https://github.com/username/my-awesome-package"
Documentation = "https://my-awesome-package.readthedocs.io"
Repository = "https://github.com/username/my-awesome-package"
"Bug Tracker" = "https://github.com/username/my-awesome-package/issues"
Changelog = "https://github.com/username/my-awesome-package/blob/main/CHANGELOG.md"
[project.scripts]
my-cli = "my_package.cli:main"
awesome-tool = "my_package.tools:run"
[project.entry-points."my_package.plugins"]
plugin1 = "my_package.plugins:plugin1"
[tool.setuptools]
package-dir = {"" = "src"}
zip-safe = false
[tool.setuptools.packages.find]
where = ["src"]
include = ["my_package*"]
exclude = ["tests*"]
[tool.setuptools.package-data]
my_package = ["py.typed", "*.pyi", "data/*.json"]
# Black configuration
[tool.black]
line-length = 100
target-version = ["py38", "py39", "py310", "py311"]
include = '\.pyi?$'
# Ruff configuration
[tool.ruff]
line-length = 100
target-version = "py38"
[tool.ruff.lint]
select = ["E", "F", "I", "N", "W", "UP"]
# MyPy configuration
[tool.mypy]
python_version = "3.8"
warn_return_any = true
warn_unused_configs = true
disallow_untyped_defs = true
# Pytest configuration
[tool.pytest.ini_options]
testpaths = ["tests"]
python_files = ["test_*.py"]
addopts = "-v --cov=my_package --cov-report=term-missing"
# Coverage configuration
[tool.coverage.run]
source = ["src"]
omit = ["*/tests/*"]
[tool.coverage.report]
exclude_lines = [
    "pragma: no cover",
    "def __repr__",
    "raise AssertionError",
    "raise NotImplementedError",
]
Pattern 5: Dynamic Versioning
[build-system]
requires = ["setuptools>=61.0", "setuptools-scm>=8.0"]
build-backend = "setuptools.build_meta"
[project]
name = "my-package"
dynamic = ["version"]
description = "Package with dynamic version"
[tool.setuptools.dynamic]
version = {attr = "my_package.__version__"}
# Or use setuptools-scm for git-based versioning
[tool.setuptools_scm]
write_to = "src/my_package/_version.py"
In init.py:
# src/my_package/__init__.py
__version__ = "1.0.0"
# Or with setuptools-scm
from importlib.metadata import version
__version__ = version("my-package")
Command-Line Interface (CLI) Patterns
Pattern 6: CLI with Click
# src/my_package/cli.py
import click
@click.group()
@click.version_option()
def cli():
    """My awesome CLI tool."""
    pass
@cli.command()
@click.argument("name")
@click.option("--greeting", default="Hello", help="Greeting to use")
def greet(name: str, greeting: str):
    """Greet someone."""
    click.echo(f"{greeting}, {name}!")
@cli.command()
@click.option("--count", default=1, help="Number of times to repeat")
def repeat(count: int):
    """Repeat a message."""
    for i in range(count):
        click.echo(f"Message {i + 1}")
def main():
    """Entry point for CLI."""
    cli()
if __name__ == "__main__":
    main()
Register in pyproject.toml:
[project.scripts]
my-tool = "my_package.cli:main"
Usage:
pip install -e .
my-tool greet World
my-tool greet Alice --greeting="Hi"
my-tool repeat --count=3
Pattern 7: CLI with argparse
# src/my_package/cli.py
import argparse
import sys
def main():
    """Main CLI entry point."""
    parser = argparse.ArgumentParser(
        description="My awesome tool",
        prog="my-tool"
    )
    parser.add_argument(
        "--version",
        action="version",
        version="%(prog)s 1.0.0"
    )
    subparsers = parser.add_subparsers(dest="command", help="Commands")
    # Add subcommand
    process_parser = subparsers.add_parser("process", help="Process data")
    process_parser.add_argument("input_file", help="Input file path")
    process_parser.add_argument(
        "--output", "-o",
        default="output.txt",
        help="Output file path"
    )
    args = parser.parse_args()
    if args.command == "process":
        process_data(args.input_file, args.output)
    else:
        parser.print_help()
        sys.exit(1)
def process_data(input_file: str, output_file: str):
    """Process data from input to output."""
    print(f"Processing {input_file} -> {output_file}")
if __name__ == "__main__":
    main()
Building and Publishing
Pattern 8: Build Package Locally
# Install build tools
pip install build twine
# Build distribution
python -m build
# This creates:
# dist/
#   my-package-1.0.0.tar.gz (source distribution)
#   my_package-1.0.0-py3-none-any.whl (wheel)
# Check the distribution
twine check dist/*
Pattern 9: Publishing to PyPI
# Install publishing tools
pip install twine
# Test on TestPyPI first
twine upload --repository testpypi dist/*
# Install from TestPyPI to test
pip install --index-url https://test.pypi.org/simple/ my-package
# If all good, publish to PyPI
twine upload dist/*
Using API tokens (recommended):
# Create ~/.pypirc
[distutils]
index-servers =
    pypi
    testpypi
[pypi]
username = __token__
password = pypi-...your-token...
[testpypi]
username = __token__
password = pypi-...your-test-token...
Pattern 10: Automated Publishing with GitHub Actions
# .github/workflows/publish.yml
name: Publish to PyPI
on:
  release:
    types: [created]
jobs:
  publish:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Set up Python
        uses: actions/setup-python@v4
        with:
          python-version: "3.11"
      - name: Install dependencies
        run: |
          pip install build twine
      - name: Build package
        run: python -m build
      - name: Check package
        run: twine check dist/*
      - name: Publish to PyPI
        env:
          TWINE_USERNAME: __token__
          TWINE_PASSWORD: ${{ secrets.PYPI_API_TOKEN }}
        run: twine upload dist/*
Advanced Patterns
Pattern 11: Including Data Files
[tool.setuptools.package-data]
my_package = [
    "data/*.json",
    "templates/*.html",
    "static/css/*.css",
    "py.typed",
]
Accessing data files:
# src/my_package/loader.py
from importlib.resources import files
import json
def load_config():
    """Load configuration from package data."""
    config_file = files("my_package").joinpath("data/config.json")
    with config_file.open() as f:
        return json.load(f)
# Python 3.9+
from importlib.resources import files
data = files("my_package").joinpath("data/file.txt").read_text()
Pattern 12: Namespace Packages
For large projects split across multiple repositories:
# Package 1: company-core
company/
└── core/
    ├── __init__.py
    └── models.py
# Package 2: company-api
company/
└── api/
    ├── __init__.py
    └── routes.py
Do NOT include init.py in the namespace directory (company/):
# company-core/pyproject.toml
[project]
name = "company-core"
[tool.setuptools.packages.find]
where = ["."]
include = ["company.core*"]
# company-api/pyproject.toml
[project]
name = "company-api"
[tool.setuptools.packages.find]
where = ["."]
include = ["company.api*"]
Usage:
# Both packages can be imported under same namespace
from company.core import models
from company.api import routes
Pattern 13: C Extensions
[build-system]
requires = ["setuptools>=61.0", "wheel", "Cython>=0.29"]
build-backend = "setuptools.build_meta"
[tool.setuptools]
ext-modules = [
    {name = "my_package.fast_module", sources = ["src/fast_module.c"]},
]
Or with setup.py:
# setup.py
from setuptools import setup, Extension
setup(
    ext_modules=[
        Extension(
            "my_package.fast_module",
            sources=["src/fast_module.c"],
            include_dirs=["src/include"],
        )
    ]
)
Version Management
Pattern 14: Semantic Versioning
# src/my_package/__init__.py
__version__ = "1.2.3"
# Semantic versioning: MAJOR.MINOR.PATCH
# MAJOR: Breaking changes
# MINOR: New features (backward compatible)
# PATCH: Bug fixes
Version constraints in dependencies:
dependencies = [
    "requests>=2.28.0,<3.0.0",  # Compatible range
    "click~=8.1.0",              # Compatible release (~= 8.1.0 means >=8.1.0,<8.2.0)
    "pydantic>=2.0",             # Minimum version
    "numpy==1.24.3",             # Exact version (avoid if possible)
]
Pattern 15: Git-Based Versioning
[build-system]
requires = ["setuptools>=61.0", "setuptools-scm>=8.0"]
build-backend = "setuptools.build_meta"
[project]
name = "my-package"
dynamic = ["version"]
[tool.setuptools_scm]
write_to = "src/my_package/_version.py"
version_scheme = "post-release"
local_scheme = "dirty-tag"
Creates versions like:
- 1.0.0(from git tag)
- 1.0.1.dev3+g1234567(3 commits after tag)
Testing Installation
Pattern 16: Editable Install
# Install in development mode
pip install -e .
# With optional dependencies
pip install -e ".[dev]"
pip install -e ".[dev,docs]"
# Now changes to source code are immediately reflected
Pattern 17: Testing in Isolated Environment
# Create virtual environment
python -m venv test-env
source test-env/bin/activate  # Linux/Mac
# test-env\Scripts\activate  # Windows
# Install package
pip install dist/my_package-1.0.0-py3-none-any.whl
# Test it works
python -c "import my_package; print(my_package.__version__)"
# Test CLI
my-tool --help
# Cleanup
deactivate
rm -rf test-env
Documentation
Pattern 18: README.md Template
# My Package
[](https://pypi.org/project/my-package/)
[](https://pypi.org/project/my-package/)
[](https://github.com/username/my-package/actions)
Brief description of your package.
## Installation
```bash
pip install my-package
Quick Start
from my_package import something
result = something.do_stuff()
Features
- Feature 1
- Feature 2
- Feature 3
Documentation
Full documentation: https://my-package.readthedocs.io
Development
git clone https://github.com/username/my-package.git
cd my-package
pip install -e ".[dev]"
pytest
License
MIT
## Common Patterns
### Pattern 19: Multi-Architecture Wheels
```yaml
# .github/workflows/wheels.yml
name: Build wheels
on: [push, pull_request]
jobs:
  build_wheels:
    name: Build wheels on ${{ matrix.os }}
    runs-on: ${{ matrix.os }}
    strategy:
      matrix:
        os: [ubuntu-latest, windows-latest, macos-latest]
    steps:
      - uses: actions/checkout@v3
      - name: Build wheels
        uses: pypa/cibuildwheel@v2.16.2
      - uses: actions/upload-artifact@v3
        with:
          path: ./wheelhouse/*.whl
Pattern 20: Private Package Index
# Install from private index
pip install my-package --index-url https://private.pypi.org/simple/
# Or add to pip.conf
[global]
index-url = https://private.pypi.org/simple/
extra-index-url = https://pypi.org/simple/
# Upload to private index
twine upload --repository-url https://private.pypi.org/ dist/*
File Templates
.gitignore for Python Packages
# Build artifacts
build/
dist/
*.egg-info/
*.egg
.eggs/
# Python
__pycache__/
*.py[cod]
*$py.class
*.so
# Virtual environments
venv/
env/
ENV/
# IDE
.vscode/
.idea/
*.swp
# Testing
.pytest_cache/
.coverage
htmlcov/
# Distribution
*.whl
*.tar.gz
MANIFEST.in
# MANIFEST.in
include README.md
include LICENSE
include pyproject.toml
recursive-include src/my_package/data *.json
recursive-include src/my_package/templates *.html
recursive-exclude * __pycache__
recursive-exclude * *.py[co]
Checklist for Publishing
- Code is tested (pytest passing)
- Documentation is complete (README, docstrings)
- Version number updated
- CHANGELOG.md updated
- License file included
- pyproject.toml is complete
- Package builds without errors
- Installation tested in clean environment
- CLI tools work (if applicable)
- PyPI metadata is correct (classifiers, keywords)
- GitHub repository linked
- Tested on TestPyPI first
- Git tag created for release
Resources
- Python Packaging Guide: https://packaging.python.org/
- PyPI: https://pypi.org/
- TestPyPI: https://test.pypi.org/
- setuptools documentation: https://setuptools.pypa.io/
- build: https://pypa-build.readthedocs.io/
- twine: https://twine.readthedocs.io/
Best Practices Summary
- Use src/ layout for cleaner package structure
- Use pyproject.toml for modern packaging
- Pin build dependencies in build-system.requires
- Version appropriately with semantic versioning
- Include all metadata (classifiers, URLs, etc.)
- Test installation in clean environments
- Use TestPyPI before publishing to PyPI
- Document thoroughly with README and docstrings
- Include LICENSE file
- Automate publishing with CI/CD