python

A set of Python coding rules covering style, naming, imports, type hints, error handling, and testing. Python is a programming language.

In plain words
What is it for?
Use it when writing or reviewing Python files, including code that uses type hints, specific errors, and pytest tests.
Why use it?
It gives developers one consistent way to write and organize Python 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/jhl-labs/vibe-project/python
Clone the repo
git clone --depth 1 https://github.com/jhl-labs/vibe-project

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 324 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 $0.00324
Opus 5 $0.00000 $0.00162
Sonnet 5 $0.00000 $0.00065
Haiku 4.5 $0.00000 $0.00032

Measured yesterday against content hash a2a7ab616008, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

python 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 yesterday.

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.mdc · 72 lines

What it actually says

Python Rules

Style Guide

  • Follow PEP 8
  • Use type hints for all function parameters and returns
  • Maximum line length: 100 characters
  • Use f-strings for formatting

Naming

  • Files: snake_case.py
  • Classes: PascalCase
  • Functions/Variables: snake_case
  • Constants: UPPER_SNAKE_CASE
  • Private: _leading_underscore

Imports

# Order: stdlib → third-party → local
import os
from typing import Optional

import requests
from fastapi import FastAPI

from app.core import config
from app.domain import User

Type Hints

def get_user(user_id: str) -> User | None:
    """Get user by ID."""
    pass

async def create_user(data: CreateUserInput) -> User:
    """Create a new user."""
    pass

Error Handling

# Use specific exceptions
class UserNotFoundError(Exception):
    def __init__(self, user_id: str):
        super().__init__(f"User not found: {user_id}")

# Handle gracefully
try:
    result = await operation()
except SpecificError as e:
    logger.error(f"Operation failed: {e}")
    raise

Testing

  • Use pytest
  • Fixtures for setup
  • Parametrize for multiple cases
  • Mock external dependencies with pytest-mock
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. yesterday First seen · 72 lines · 0 tokens per session scan A a2a7ab616008

Subscribe to this mod's changes

python is a cursor rule published in the GitHub repository jhl-labs/vibe-project (2 stars, last pushed 7mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 324 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.