SKILL.md
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.pyMinimal 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.mdAdvantages:
- 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.pySimpler 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=3Pattern 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/*For advanced patterns including data files, namespace packages, C extensions, version management, testing installation, documentation templates, and distribution workflows, see references/advanced-patterns.md