Python Packaging

When to use this skill

Use Python Packaging when an AI agent needs a reusable SKILL.md workflow for this job: Create distributable Python packages with proper project structure, setup.py/pyproject.toml, and publishing to PyPI. Use when packaging Python libraries, creating CLI tools, or distributing Python code.

When not to use it

Skip Python Packaging when the task is outside the coding category, or when a more specific skill in this directory already covers the same workflow with clearer triggers.

How to install

1. Personal install: create ~/.claude/skills/python-packaging/SKILL.md (and any bundled scripts) so Claude Code, Claude Desktop, and compatible agents can load it in every project.
2. Project install: commit the same folder at .claude/skills/python-packaging/ so teammates get the skill with the repo.
3. Restart the agent session after copying files so it re-scans the skills directory, then ask for the task in words that match the skill description.

Full install guide for Claude, Cursor, and Codex

What this skill does

# 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

```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 = "[email protected]"}] 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:**

```toml [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/ ```

## Detailed patterns and worked examples

Detailed pattern documentation lives in `references/details.md`. Read that file when the navigation tier above is insufficient.

Intended uses

• 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