modern-python-guidance 0.2.0

Version-aware BAD/GOOD pattern guides that help AI coding agents generate modern Python

modern-python-guidance

LLMs often produce outdated Python — typing.List instead of list, @validator instead of @field_validator, setup.py instead of pyproject.toml. This tool provides 39 version-aware BAD/GOOD pattern guides that show the modern replacement, filtered by your project's Python version.

Note: The tool itself requires Python 3.11+ to run. Guides cover patterns from Python 3.9 onward, and --python-version filters guides for your target environment.

Quick start

# Install
pip install modern-python-guidance

# Search for a pattern
mpg search "pydantic validator"
#   pydantic-v2-validators                   score=18.0  [pydantic]

# Get the full guide
mpg retrieve pydantic-v2-validators
# --- pydantic-v2-validators (version match: YES) ---
# ## BAD
# @validator("name")
# ...
# ## GOOD
# @field_validator("name")
# ...

mpg is the short alias for modern-python-guidance. Both work.

CLI usage

# Search guides by keyword
mpg search "pydantic validator"

# Retrieve a specific guide (full BAD/GOOD content)
mpg retrieve use-builtin-generics

# List all guides compatible with your Python version
mpg list --python-version 3.11

# Auto-detect project Python version from pyproject.toml / .python-version
mpg detect-version

# Filter by category
mpg search "timeout" --category async

# JSON output (default when piped, explicit with --format)
mpg search "typing" --format json | jq '.[0].id'

Guide coverage

39 guides across 3 layers:

Layer	Categories	Count	Examples
1 — stdlib	typing, async, stdlib, data-structures	16	list over List, match/case, TaskGroup
2 — frameworks	pydantic, fastapi, httpx, django, sqlalchemy, pytest	18	Pydantic V2 migration, SQLAlchemy 2.0 style, Annotated[Depends]
3 — toolchain	toolchain	5	uv over pip, ruff over flake8, pickle avoidance

Run mpg list to see all 39 guides, or browse them on GitHub.

Version-aware filtering

Guides specify their minimum Python version. The CLI auto-detects your project's version from (in order):

1. --python-version flag
2. pyproject.toml requires-python
3. .python-version file
4. Default: 3.11

# Only shows guides compatible with Python 3.9
mpg list --python-version 3.9
# Excludes: TaskGroup (3.11+), match/case (3.10+), etc.

MCP server

mpg includes a built-in MCP server that exposes all 4 commands as tools. AI agents (Claude Code, Cursor, Gemini CLI, etc.) can discover and call them directly.

Setup with Claude Code

claude mcp add mpg -- mpg mcp

Or add to .mcp.json manually:

{
  "mcpServers": {
    "mpg": {
      "command": "mpg",
      "args": ["mcp"]
    }
  }
}

Available tools

Tool	Description
search_guides	Search guides by keyword with fuzzy matching
retrieve_guides	Get full BAD/GOOD content by guide ID
list_guides	Browse all guides, filter by category/version
detect_python_version	Auto-detect project Python version

The MCP server uses stdio transport (JSON-RPC 2.0) and adds zero additional dependencies.

Agent Skills integration

This project doubles as a Claude Code Agent Skills plugin. Install it into your project's .claude/skills/ to give Claude automatic access to modern Python patterns when writing or reviewing code.

# Find where the package is installed
SKILL_DIR=$(python -c "from pathlib import Path; import modern_python_guidance; print(Path(modern_python_guidance.__file__).parent / 'skills' / 'modern-python-guidance')")

# Symlink into your project
ln -s "$SKILL_DIR" your-project/.claude/skills/modern-python-guidance

For other AI tools (Cursor, Copilot, etc.), use the CLI directly — pipe mpg search or mpg retrieve output into your workflow.

Development

git clone https://github.com/yottayoshida/modern-python-guidance.git
cd modern-python-guidance
uv venv && source .venv/bin/activate
uv pip install -e ".[dev]"
pytest
ruff check src/ tests/

Project structure

src/modern_python_guidance/
├── cli.py              # Entry point (search, retrieve, list, detect-version, mcp)
├── mcp_server.py       # MCP server (JSON-RPC 2.0 over stdio)
├── frontmatter.py      # YAML-subset parser (no PyYAML dependency)
├── guide_index.py      # Guide discovery and indexing
├── search.py           # Weighted keyword search + fuzzy fallback
├── retrieve.py         # Guide retrieval and JSON rendering
├── version_detect.py   # Python version auto-detection
└── compat.py           # Shared helpers

skills/modern-python-guidance/
├── SKILL.md            # Agent Skills plugin entry point
└── guides/             # 39 guide files by category

See docs/design.md for the full design document.

Contributing

Contributions welcome! To add a new guide:

1. Create skills/modern-python-guidance/guides/<category>/<id>.md
2. Include YAML frontmatter with these fields:

Field	Type	Values
id	string	Unique kebab-case identifier (must match filename)
title	string	Short descriptive title
category	string	Must match parent directory name
layer	int	1 (stdlib), 2 (frameworks), 3 (toolchain)
tags	list	Search keywords
aliases	list	Alternate names (old API names, etc.)
python	string	Minimum version, e.g. ">=3.11"
frequency	string	high (LLMs do this often), medium, low

3. Write BAD/GOOD/Why/Version Notes sections
4. Run pytest to verify the guide parses correctly

License

Apache-2.0 OR MIT — see LICENSE and LICENSE-MIT.