python-developer

A set of guidelines for building Python software, including web services, APIs, database access, background jobs, and tests.

In plain words
What is it for?
Use it to build or modify FastAPI and Django services, REST APIs, async code, SQLAlchemy database work, Celery jobs, and pytest tests.
Why use it?
It gives the coding agent consistent Python patterns and project conventions, reducing guesswork when creating or changing backend code.

Skill for Claude CodeCodex

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 skills/mtnyilmaz/agents/python-developer
Any agent
npx skills add mtnyilmaz/agents --skill python-developer
Clone the repo
git clone --depth 1 https://github.com/mtnyilmaz/agents

Made for: Claude Code, Codex.

Per session 61 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,515 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 $0.00061 $0.01515
Opus 5 $0.00030 $0.00758
Sonnet 5 $0.00012 $0.00303
Haiku 4.5 $0.00006 $0.00152

Measured yesterday against content hash a69f4aec25b4, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

python-developer 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.

.agents/skills/python-developer/SKILL.md · 211 lines

How it starts

The opening of the file, as written. The whole thing — 211 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Python Developer

Expert in building production-grade Python services.

Reference Rules

Load these rules for the relevant context:

  • .agents/layers/language/python/python-patterns.md — Python type hints, Pydantic, async patterns
  • .agents/layers/framework/django/django-patterns.md — FastAPI and Django patterns
  • .agents/layers/concern/backend/api-design.md — REST API design principles
  • .agents/layers/universal/security-baseline.md — security requirements

Project Stack (Modern Python 2026)

Tool Purpose
Python 3.12+ Language (always latest stable)
FastAPI HTTP framework (new services)
SQLAlchemy 2.x ORM (async-first)
Alembic Database migrations
Pydantic v2 Validation & settings
pydantic-settings Environment config
asyncpg PostgreSQL async driver
Redis (aioredis) Cache + sessions
Celery + Redis Background tasks
structlog Structured logging
pytest + pytest-asyncio Testing
mypy (strict) Type checking
ruff Linting + formatting

FastAPI Application Setup

# main.py
from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware
from contextlib import asynccontextmanager
from .core.database import init_db
from .core.config import settings
from .core.errors import register_exception_handlers
from .api.v1 import router as v1_router

@asynccontextmanager
async def lifespan(app: FastAPI):
    await init_db()          # startup: create connection pool
    yield
    await close_db()         # shutdown: close connections

app = FastAPI(
    title="Service Name",
    version="1.0.0",
    lifespan=lifespan,
    docs_url="/api/docs" if settings.debug else None,  # hide docs in prod
)

app.add_middleware(
    CORSMiddleware,
    allow_origins=settings.cors_origins,   # never ["*"] in production
    allow_methods=["GET", "POST", "PUT", "PATCH", "DELETE"],
    allow_headers=["Authorization", "Content-Type"],
    allow_credentials=True,
)

register_exception_handlers(app)
app.include_router(v1_router, prefix="/api/v1")

Read the full file on GitHub · 211 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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 · 211 lines · 61 tokens per session scan A a69f4aec25b4

Subscribe to this mod's changes

python-developer is a skill published in the GitHub repository mtnyilmaz/agents (6 stars, last pushed 3mo ago), licensed MIT. It adds 61 tokens to every session and 1,515 once invoked, about $0.0003 per session on Opus 5. 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.

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