python-packaging

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Configure Python package metadata, setup.py, and pyproject.toml for distribution using UV or setuptools. Use when setting up Python packages, configuring build systems, or preparing projects for PyPI publication.

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npx skill4agent add armanzeroeight/fastagent-plugins python-packaging

Python Packaging

Configure Python package metadata and build configuration for distribution.

Quick Start

Create pyproject.toml with UV or setuptools configuration for package distribution.

Instructions

Choosing Build System

Use UV with pyproject.toml (recommended) when:
  • Starting new projects
  • Want fast, modern tooling
  • Need dependency management + packaging
  • Building libraries for PyPI
  • Want PEP 621 compliance
Use setuptools (pyproject.toml + setup.py) when:
  • Maintaining existing projects
  • Need compatibility with older tools
  • Require custom build steps
  • Complex C extensions
Use setuptools (pyproject.toml only) when:
  • Modern setuptools-only approach
  • No custom build logic
  • Want declarative configuration
  • PEP 621 compliance

UV Configuration (Recommended)

Create
pyproject.toml
with UV (PEP 621 standard):
toml
[project]
name = "my-package"
version = "0.1.0"
description = "Package description"
readme = "README.md"
requires-python = ">=3.9"
license = {text = "MIT"}
authors = [
    {name = "Your Name", email = "you@example.com"}
]
keywords = ["keyword1", "keyword2"]
classifiers = [
    "Development Status :: 3 - Alpha",
    "Intended Audience :: Developers",
    "License :: OSI Approved :: MIT License",
    "Programming Language :: Python :: 3",
    "Programming Language :: Python :: 3.9",
    "Programming Language :: Python :: 3.10",
    "Programming Language :: Python :: 3.11",
]
dependencies = [
    "requests>=2.28.0",
]

[project.optional-dependencies]
dev = [
    "pytest>=7.0.0",
    "black>=23.0.0",
    "mypy>=1.0.0",
]

[project.scripts]
my-cli = "my_package.cli:main"

[project.urls]
Homepage = "https://github.com/username/my-package"
Repository = "https://github.com/username/my-package"

[build-system]
requires = ["hatchling"]
build-backend = "hatchling.build"
Key fields:
  • name
    : Package name (use hyphens, will be converted to underscores for import)
  • version
    : Semantic versioning (MAJOR.MINOR.PATCH)
  • requires-python
    : Python version constraint
  • dependencies
    : Runtime dependencies with version constraints
  • optional-dependencies
    : Development and optional dependencies
  • scripts
    : Console script entry points
Version constraints:
  • >=2.28.0,<3.0.0
    : Compatible versions
  • ~=2.28.0
    : >=2.28.0, <2.29.0 (patch updates)
  • >=2.28.0
    : Minimum version
  • ==2.28.0
    : Exact version

Setuptools Configuration (Modern)

Create
pyproject.toml
with setuptools (PEP 621):
toml
[build-system]
requires = ["setuptools>=61.0", "wheel"]
build-backend = "setuptools.build_meta"

[project]
name = "my-package"
version = "0.1.0"
description = "Package description"
readme = "README.md"
requires-python = ">=3.9"
license = {text = "MIT"}
authors = [
    {name = "Your Name", email = "you@example.com"}
]
keywords = ["keyword1", "keyword2"]
classifiers = [
    "Development Status :: 3 - Alpha",
    "Intended Audience :: Developers",
    "License :: OSI Approved :: MIT License",
    "Programming Language :: Python :: 3",
]
dependencies = [
    "requests>=2.28.0",
]

[project.optional-dependencies]
dev = [
    "pytest>=7.0.0",
    "black>=23.0.0",
    "mypy>=1.0.0",
]

[project.scripts]
my-cli = "my_package.cli:main"

[project.urls]
Homepage = "https://github.com/username/my-package"
Repository = "https://github.com/username/my-package"

Setuptools Configuration (Legacy)

Create
setup.py
for projects requiring custom build logic:
python
from setuptools import setup, find_packages

setup(
    name="my-package",
    version="0.1.0",
    description="Package description",
    long_description=open("README.md").read(),
    long_description_content_type="text/markdown",
    author="Your Name",
    author_email="you@example.com",
    url="https://github.com/username/my-package",
    packages=find_packages(where="src"),
    package_dir={"": "src"},
    python_requires=">=3.9",
    install_requires=[
        "requests>=2.28.0",
    ],
    extras_require={
        "dev": [
            "pytest>=7.0.0",
            "black>=23.0.0",
            "mypy>=1.0.0",
        ],
    },
    entry_points={
        "console_scripts": [
            "my-cli=my_package.cli:main",
        ],
    },
    classifiers=[
        "Development Status :: 3 - Alpha",
        "Intended Audience :: Developers",
        "License :: OSI Approved :: MIT License",
        "Programming Language :: Python :: 3",
    ],
)
When to use setup.py:
  • Custom build steps (compiling C extensions)
  • Dynamic version from git tags
  • Complex package discovery
  • Conditional dependencies

Package Structure

Flat layout:
my-package/
├── my_package/
│   ├── __init__.py
│   └── module.py
├── tests/
├── pyproject.toml
└── README.md
Src layout (recommended for libraries):
my-package/
├── src/
│   └── my_package/
│       ├── __init__.py
│       └── module.py
├── tests/
├── pyproject.toml
└── README.md
For src layout, configure package discovery:
UV/Hatchling (pyproject.toml):
toml
[tool.hatch.build.targets.wheel]
packages = ["src/my_package"]
Setuptools (pyproject.toml):
toml
[tool.setuptools.packages.find]
where = ["src"]
Setuptools (setup.py):
python
packages=find_packages(where="src"),
package_dir={"": "src"},

Version Management

Static version in pyproject.toml:
toml
[project]
version = "0.1.0"
Dynamic version from file:
toml
[project]
dynamic = ["version"]

[tool.setuptools.dynamic]
version = {attr = "my_package.__version__"}
Then in
src/my_package/__init__.py
:
python
__version__ = "0.1.0"
Dynamic version from git tags (requires setup.py):
python
from setuptools import setup
from setuptools_scm import get_version

setup(
    use_scm_version=True,
    setup_requires=["setuptools_scm"],
)

Entry Points and Scripts

Console scripts create command-line tools:
toml
[project.scripts]
my-cli = "my_package.cli:main"
another-tool = "my_package.tools:run"
This creates executables that call the specified functions.
Entry point function:
python
# my_package/cli.py
def main():
    print("Hello from my-cli!")
    
if __name__ == "__main__":
    main()

Including Data Files

Include package data:
toml
[tool.setuptools.package-data]
my_package = ["data/*.json", "templates/*.html"]
Include non-package files:
Create
MANIFEST.in
:
include README.md
include LICENSE
recursive-include src/my_package/data *

Classifiers

Use PyPI classifiers to categorize your package:
toml
classifiers = [
    # Development status
    "Development Status :: 3 - Alpha",
    "Development Status :: 4 - Beta",
    "Development Status :: 5 - Production/Stable",
    
    # Audience
    "Intended Audience :: Developers",
    "Intended Audience :: Science/Research",
    
    # License
    "License :: OSI Approved :: MIT License",
    
    # Python versions
    "Programming Language :: Python :: 3",
    "Programming Language :: Python :: 3.9",
    "Programming Language :: Python :: 3.10",
    "Programming Language :: Python :: 3.11",
    
    # Topics
    "Topic :: Software Development :: Libraries",
    "Topic :: Internet :: WWW/HTTP",
]

Building and Publishing

With UV (recommended):
bash
# Build distribution
uv build

# Publish to PyPI
uv publish

# Or use twine
uv build
twine upload dist/*
With setuptools:
bash
# Install build tools
pip install build twine

# Build distribution
python -m build

# Publish to PyPI
twine upload dist/*

Testing Installation

Test your package locally before publishing:
bash
# Install in editable mode with UV
uv pip install -e .

# Or with pip
pip install -e .

# Test the package
python -c "import my_package; print(my_package.__version__)"

# Test console scripts
my-cli --help

Common Patterns

Multi-Package Project

For projects with multiple packages:
toml
[tool.hatch.build.targets.wheel]
packages = ["src/package1", "src/package2"]

Optional Dependencies

Group optional features:
toml
[project.optional-dependencies]
dev = ["pytest", "black", "mypy"]
docs = ["sphinx", "sphinx-rtd-theme"]
aws = ["boto3"]
all = ["pytest", "black", "mypy", "sphinx", "boto3"]
Install with:
pip install my-package[dev]
or
pip install my-package[all]

Platform-Specific Dependencies

toml
[project]
dependencies = [
    "requests",
    "pywin32; platform_system=='Windows'",
    "python-daemon; platform_system=='Linux'",
]

Validation

Before publishing, verify:
  1. Package builds successfully:
    bash
    uv build  # or python -m build
  2. Metadata is correct:
    bash
    twine check dist/*
  3. Installation works:
    bash
    uv pip install dist/*.whl
  4. Entry points work:
    bash
    my-cli --version
  5. Imports work:
    python
    import my_package
    print(my_package.__version__)

Troubleshooting

Package not found after installation:
  • Check package name vs. import name (hyphens vs. underscores)
  • Verify package discovery configuration
  • Ensure
    __init__.py
    exists in package directory
Entry points not working:
  • Verify function signature (should take no arguments or use argparse)
  • Check entry point syntax:
    "script-name = "package.module:function"
  • Reinstall package after changes
Data files not included:
  • Add to
    package-data
    in pyproject.toml
  • Or create MANIFEST.in
  • Verify with:
    python -m tarfile -l dist/*.tar.gz
Version conflicts:
  • Use compatible version constraints (
    >=,<
    syntax)
  • Test with different dependency versions
  • UV automatically creates lock files for reproducibility