python-development

A set of guidelines for modern Python development, covering web applications, asynchronous code, data science, and machine learning.

In plain words
What is it for?
Use it when creating or modifying Python projects, including FastAPI or Django applications, scripts, data-processing code, and ML work.
Why use it?
It makes the agent check the existing project and Python tools first, use an isolated environment, and follow consistent project practices before editing code.

Cursor rule for Cursor

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add rules/madebyaris/rakitui-ai/python-development
Clone the repo
git clone --depth 1 https://github.com/madebyaris/rakitui-ai

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 3,606 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.03606
Opus 5 $0.00000 $0.01803
Sonnet 5 $0.00000 $0.00721
Haiku 4.5 $0.00000 $0.00361

Measured 2d ago against content hash 6f607b95f0b3, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

python-development scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.cursor/rules/python-development.mdc · 644 lines

How it starts

The opening of the file, as written. The whole thing — 644 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Python Development Patterns

Modern Python (3.10+) best practices for web development, data science, and general programming.

CRITICAL: Agentic-First Python Development

Pre-Development Verification (MANDATORY)

Before writing ANY Python code:

1. CHECK PYTHON INSTALLATION
   → run_terminal_cmd("python3 --version")
   → run_terminal_cmd("pip --version")
   → run_terminal_cmd("uv --version")  # Modern package manager
   
2. VERIFY CURRENT VERSIONS (use web_search)
   → web_search("Python stable version December 2024")
   → web_search("FastAPI latest version 2024")
   → web_search("Django LTS version 2024")
   
3. CHECK EXISTING PROJECT
   → Does pyproject.toml/requirements.txt exist? Read it first!
   → Is there a virtual environment?
   → What dependencies are already installed?
   
4. VIRTUAL ENVIRONMENT (ALWAYS USE)
   → run_terminal_cmd("python3 -m venv .venv")
   → run_terminal_cmd("source .venv/bin/activate")

CLI-First Python Development

ALWAYS use CLI for package management:

# Virtual environment (ALWAYS create first)
python3 -m venv .venv
source .venv/bin/activate  # Unix
.venv\Scripts\activate  # Windows

# Modern: uv (10-100x faster than pip)
uv venv
uv pip install fastapi uvicorn
uv pip sync requirements.txt

# Traditional: pip
pip install fastapi uvicorn
pip install -r requirements.txt
pip freeze > requirements.txt

# Framework CLIs (use these for scaffolding)
# Django
django-admin startproject myproject
python manage.py startapp myapp

# FastAPI with cookiecutter
pip install cookiecutter
cookiecutter https://github.com/tiangolo/full-stack-fastapi-template

# Poetry (if project uses it)
poetry init
poetry add fastapi
poetry install

Post-Edit Verification

After ANY Python code changes:

# Type checking
mypy src/

# Linting
ruff check .
ruff format --check .

# Or older tools
flake8 .
black --check .

# Tests
pytest
pytest --cov=src

# Verify imports work
python -c "import mypackage"

Common Python Syntax Traps (Avoid These!)

Read the full file on GitHub · 644 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 644 lines · 0 tokens per session scan A 6f607b95f0b3

Subscribe to this mod's changes

python-development is a cursor rule published in the GitHub repository madebyaris/rakitui-ai (5 stars, last pushed 7mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 3,606 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.