name: python description: Adaptive Python development guide with tiered complexity levels (Minimal/Standard/Full). Automatically selects appropriate guidance based on project context - from simple scripts (just clean Python code) to full production systems (complete tooling ecosystem). Covers modern conventions, testing, tooling, security, and best practices. Use when writing Python code, converting scripts, setting up projects, or building production systems. Keywords: PEP-8, Ruff, pytest, mypy, simple scripts, project structure, PyPI, packaging, type hints, clean code allowed-tools: Read, Bash, Glob, Grep

Python Development Skill

Comprehensive guide to modern Python development covering conventions, testing, tooling, security, performance, and ecosystem best practices (2024-2025 standards).

Tier 2 Quick Start

For multi-file projects, team collaboration, and maintained code:

# Install Python 3.12 and uv (see Installation guides)
# Windows: winget install Python.Python.3.12 && winget install astral-sh.uv
# macOS: brew install python@3.13 uv
# Linux: apt install python3.13 && curl -LsSf https://astral.sh/uv/install.sh | sh

# Create new project with modern structure
uv init my-project
cd my-project

# Add dependencies
uv add requests httpx pydantic

# Add development dependencies
uv add --dev pytest pytest-cov ruff mypy

# Set up code quality (create pyproject.toml config - see assets/pyproject-toml-template.toml)
# Configure Ruff, mypy, pytest

# Write tests (pytest)
# tests/test_example.py - mirror src/ structure

# Run quality checks
uv run ruff check .          # Linting
uv run ruff format .         # Formatting
uv run mypy .                # Type checking
uv run pytest                # Run tests
uv run pytest --cov          # With coverage

When to Use This Skill

Invoke this skill when you need guidance on:

Installation & Setup: Installing Python 3.12/3.14, uv, setting up development environment
Code Style: Following PEP-8, configuring Ruff/Black, naming conventions
Project Structure: Organizing code with src/ layout, imports, package structure
Dependency Management: Using uv, Poetry, pip, virtual environments, pyproject.toml
Testing: Writing pytest tests, fixtures, parametrization, coverage, mocking
Type Hints: Modern typing patterns, mypy configuration, protocols, generics
Code Quality: Setting up Ruff, mypy, Bandit, pre-commit hooks, CI/CD
Async Programming: asyncio patterns, async/await, TaskGroup, structured concurrency
Security: OWASP best practices, input validation, dependency scanning
Performance: Profiling, optimization patterns, Cython
Packaging: pyproject.toml, PyPI publishing, versioning, distribution
Common Libraries: Standard library essentials, ecosystem overview
Documentation: Docstrings (PEP-257), Sphinx, documentation generation

Overview

This skill provides modern Python development guidance aligned with current best practices (2024-2025):

Core Standards:

Style: PEP-8 (enforced via Ruff)
Type Hints: PEP-484, PEP-526, modern syntax (PEP-604: str | None)
Packaging: PEP-517, PEP-518 (pyproject.toml)
Docstrings: PEP-257
Testing: pytest (industry standard)
Dependency Management: uv (fastest) or Poetry (feature-rich)

Modern Tooling (2024-2025):

Linter/Formatter: Ruff (replaces flake8, isort, optionally Black)
Type Checker: mypy with strict mode
Test Framework: pytest
Dependency Manager: uv or Poetry
Security Scanner: Bandit + pip-audit
Project Config: pyproject.toml (universal)

Project Structure:

src/ layout (modern standard, not flat layout)
Absolute imports preferred over relative
Tests mirror src/ structure
pyproject.toml for all configuration

Official Sources: All guidance backed by official Python documentation, PEPs, and tool documentation:

docs.python.org
peps.python.org
docs.astral.sh/ruff
docs.astral.sh/uv
mypy-lang.org
docs.pytest.org

Quick Tier Selection

Choose your complexity level:

🎯 Tier 1: Minimal (Simple Scripts)

→ Single-file utilities, converting scripts, one-off automation → Just Python code - no tooling overhead → Jump to Minimal Guidance

📦 Tier 2: Standard (Organized Projects)

→ Multi-file modules, team projects, maintained code → Modern project structure + testing → Jump to Standard Guidance

🚀 Tier 3: Full (Production Systems)

→ PyPI packages, enterprise systems, production deployments → Complete tooling ecosystem → Jump to Full Guidance

Not sure? Default to Tier 2 (Standard) - it covers most use cases.

Tier 1: Minimal (Simple Scripts)

For: Single-file utilities, script conversions, and simple automation.

Setup

Just Python 3.12+ - no additional tooling required:

✅ No uv, no virtual environment needed
✅ No pyproject.toml, no src/ layout
✅ Optional: Install Ruff for quick linting (pip install ruff)

Code Standards

Follow these simple principles:

PEP-8 naming: snake_case for functions/variables, PascalCase for classes
Type hints: Add for clarity (helps readers understand your code)
Docstrings: Simple descriptions of what functions do
pathlib: Use pathlib.Path for file operations (not os.path)
Built-ins: Use Python's built-in json, datetime, sys modules

Example: Simple Logging Script

#!/usr/bin/env python3
"""Simple logging utility - converts event to JSON."""

import json
import sys
from datetime import datetime, timezone
from pathlib import Path


def log_event(event_name: str, data: dict) -> None:
    """
    Log an event to daily JSONL file.

    Args:
        event_name: Name of the event
        data: Event data to log
    """
    log_dir = Path(__file__).parent / "logs"
    log_dir.mkdir(exist_ok=True)

    now = datetime.now(timezone.utc)
    log_file = log_dir / f"{now:%Y-%m-%d}.jsonl"

    entry = {
        "timestamp": now.isoformat(),
        "event": event_name,
        "data": data
    }

    with open(log_file, "a", encoding="utf-8") as f:
        f.write(json.dumps(entry) + "\n")


if __name__ == "__main__":
    if len(sys.argv) < 2:
        print("Usage: script.py <event_name>", file=sys.stderr)
        sys.exit(1)
    event_name = sys.argv[1]
    data = json.loads(sys.stdin.read())
    log_event(event_name, data)

Optional: Quick Linting

If you want to check your code style:

# Install Ruff (optional)
pip install ruff

# Check code
ruff check script.py

# Format code
ruff format script.py

When to Upgrade to Tier 2

Consider upgrading to Tier 2 (Standard) when:

✅ Script grows to 3+ files
✅ Multiple people working on code
✅ Need automated testing
✅ Managing external dependencies
✅ Code will be maintained long-term

Tier 2: Standard (Organized Projects)

For: Multi-file modules, team projects, and maintained code.

Modern Python project setup with proper structure, testing, and quality tools.

Installation

Install Python 3.12+ and uv (modern dependency manager). See platform-specific guides:

Installation Overview - Concepts and version policy
Windows Installation - WinGet, Python Launcher
macOS Installation - Homebrew installation
Linux Installation - apt/dnf or build from source

Project Setup and Organization

Conventions and Style - Follow PEP-8 with Ruff for linting and formatting:

See Conventions and Style Guide

Project Structure - Use modern src/ layout for proper packaging:

See Project Structure Guide

Dependency Management - Choose between uv (fastest), Poetry (feature-rich), or pip+venv:

See Dependency Management Guide

Testing and Quality

Testing - Use pytest with fixtures, parametrization, and coverage:

See Testing Methodology Guide

Type Hints - Modern typing with mypy, protocols, and generics:

See Type Hints Guide

Code Quality - Set up Ruff, mypy, Bandit, and pre-commit hooks:

See Code Quality Tools Guide

Advanced Development

Async Programming - asyncio patterns, TaskGroup, structured concurrency:

See Async Patterns Guide

Security - OWASP best practices, input validation, secrets management:

See Security Best Practices Guide

Performance - Profiling, optimization patterns, memory efficiency:

See Performance Optimization Guide

Packaging - Publish to PyPI with pyproject.toml and semantic versioning:

See Packaging and Distribution Guide

Libraries - Standard library essentials and ecosystem overview:

See Common Libraries Guide

Documentation - PEP-257 docstrings, Sphinx, ReadTheDocs:

See Docstrings and Documentation Guide

Tier 3: Full (Production Systems)

For: PyPI packages, enterprise systems, and production deployments.

Everything in Tier 2 (Standard) PLUS:

Security & Quality

Security scanning: Bandit for code security, pip-audit for dependency vulnerabilities
Pre-commit hooks: Automated checks before every commit
Comprehensive type coverage: mypy strict mode across entire codebase
Code coverage enforcement: Minimum coverage requirements in CI/CD

Distribution

PyPI packaging: Build and publish Python packages to PyPI
Semantic versioning: Follow semver for version management
Binary distributions: Create wheels for faster installation
Multi-platform support: Test and build for Windows/macOS/Linux

CI/CD

GitHub Actions / GitLab CI: Automated testing on every push
Multi-version testing: Test against Python 3.12, 3.13, 3.14
Coverage tracking: Automated coverage reports and enforcement
Release automation: Automatic PyPI publishing on tags

Documentation

Sphinx: Generate API documentation from docstrings
ReadTheDocs: Host documentation with versioning
Comprehensive docstrings: Google or NumPy style for all public APIs
Examples and tutorials: User-facing documentation with examples

Detailed Guides

See these reference files for comprehensive production guidance:

Security Best Practices - OWASP, Bandit, pip-audit
Packaging and Distribution - PyPI publishing, versioning
Code Quality Tools - Pre-commit hooks, CI/CD setup
Docstrings and Documentation - Sphinx, ReadTheDocs

Reference Files

All detailed guidance is in the references/ directory:

Installation:

Installation Overview - Platform-independent concepts
Windows Installation - Python + uv on Windows
macOS Installation - Python + uv on macOS
Linux Installation - Python + uv on Linux

Core Development:

Conventions and Style - PEP-8, Ruff, Black, naming
Project Structure - src/ layout, imports, organization
Dependency Management - uv, Poetry, pip, venv
Testing Methodology - pytest, fixtures, coverage
Type Hints - Modern typing, mypy, protocols
Code Quality Tools - Ruff, mypy, Bandit setup

Advanced Topics:

Async Patterns - asyncio, TaskGroup, structured concurrency
Security Best Practices - OWASP, validation, scanning
Performance Optimization - Profiling, patterns, Cython
Packaging and Distribution - pyproject.toml, PyPI, versioning
Common Libraries - Standard library + ecosystem essentials
Docstrings and Documentation - PEP-257, Sphinx

Assets

Template Files:

pyproject.toml Template - Modern project configuration template

Testing and Evaluation

This skill includes formal evaluation scenarios to validate effectiveness:

See Skill Evaluation Scenarios for test cases covering:
- Minimal Tier (simple scripts)
- Standard Tier (new projects, code quality tools)
- Full Tier (production systems)
- Alternative workflows (Poetry vs uv)
- Success criteria and testing methodology

Related Skills

git-commit: Git commit workflow (complements Python project workflow)
git:config: Git configuration (Python projects use Git)
code-quality:markdown-linting: Markdown linting via plugin (Python projects have READMEs)

Version History

1.1.2 (2025-11-25): Comprehensive improvements
- Fixed deprecated datetime.utcnow() in example code (use datetime.now(timezone.utc))
- Added Python 3.13 coverage (was missing between 3.12 and 3.14)
- Updated PEP URLs to modern format (peps.python.org instead of python.org/dev/peps/)
- Added UTF-8 encoding to file open in example code
- Added error handling for missing CLI arguments in example
1.1.1 (2025-11-25): Version audit update
- Updated tool version references (Ruff 0.14.x, mypy 1.18.x, pytest 9.x)
- Verified all reference file links exist and are correct
- Validated YAML frontmatter against official requirements
1.1.0 (2025-11-18): Adaptive tiered guidance
- Added three-tier complexity system (Minimal/Standard/Full)
- Tier 1: Minimal guidance for simple scripts (no tooling overhead)
- Tier 2: Standard guidance for organized projects (original Quick Start)
- Tier 3: Full guidance for production systems (comprehensive tooling)
- Context-aware skill automatically selects appropriate tier based on query
- Prevents "big bang" overengineering for simple scenarios
1.0.0 (2025-11-17): Initial release
- Comprehensive modern Python guidance (2024-2025 standards)
- Migrated installation docs from docs/python/
- Added 12 detailed reference files
- Modern tooling: Ruff, uv, pytest, mypy
- pyproject.toml template

Official Documentation

Python:

Official Python Documentation: https://docs.python.org/
Python 3.12 What's New: https://docs.python.org/3.12/whatsnew/3.12.html
Python 3.13 What's New: https://docs.python.org/3.13/whatsnew/3.13.html
Python 3.14 What's New: https://docs.python.org/3.14/whatsnew/3.14.html
Python Enhancement Proposals (PEPs): https://peps.python.org/

Tools:

uv Documentation: https://docs.astral.sh/uv/
Ruff Documentation: https://docs.astral.sh/ruff/
mypy Documentation: https://mypy-lang.org/
pytest Documentation: https://docs.pytest.org/
Poetry Documentation: https://python-poetry.org/docs/

PEPs (Python Enhancement Proposals):

PEP-8 (Style Guide): https://peps.python.org/pep-0008/
PEP-257 (Docstring Conventions): https://peps.python.org/pep-0257/
PEP-484 (Type Hints): https://peps.python.org/pep-0484/
PEP-517 (Build System): https://peps.python.org/pep-0517/
PEP-518 (pyproject.toml): https://peps.python.org/pep-0518/
PEP-604 (Union Types with |): https://peps.python.org/pep-0604/

Last Updated

Date: 2025-11-28 Model: claude-opus-4-5-20251101

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Python Development Skill

Tier 2 Quick Start

When to Use This Skill

Overview

Quick Tier Selection

🎯 Tier 1: Minimal (Simple Scripts)

📦 Tier 2: Standard (Organized Projects)

🚀 Tier 3: Full (Production Systems)

Tier 1: Minimal (Simple Scripts)

Setup

Code Standards

Example: Simple Logging Script

Optional: Quick Linting

When to Upgrade to Tier 2

Tier 2: Standard (Organized Projects)

Installation

Project Setup and Organization

Testing and Quality

Advanced Development

Tier 3: Full (Production Systems)

Security & Quality

Distribution

CI/CD

Documentation

Detailed Guides

Reference Files

Assets

Testing and Evaluation

Related Skills

Version History

Official Documentation

Last Updated

Repository

Actions

Related Skills