fastapi-patterns

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• SKILL.md

SKILL.md (first lines)

# FastAPI Patterns

Build production-ready async APIs with FastAPI's dependency injection and type system.

## Project Layout

```
src/
├── app/
│   ├── __init__.py
│   ├── main.py           # FastAPI app factory
│   ├── config.py          # Pydantic Settings
│   ├── dependencies.py    # Shared DI providers
│   ├── middleware.py       # Custom middleware
│   ├── routers/
│   │   ├── __init__.py
│   │   ├── skills.py
│   │   └── registry.py
│   ├── models/
│   │   ├── __init__.py
│   │   ├── skill.py       # Pydantic models
│   │   └── registry.py
│   ├── services/
│   │   ├── __init__.py
│   │   ├── skill_service.py
│   │   └── registry_service.py
│   └── db/
│       ├── __init__.py
│       └── session.py
└── tests/
    ├── conftest.py
    └── test_skills.py
```

## App Factory

```python
from fastapi import FastAPI
from contextlib import asynccontextmanager

@asynccontextmanager
async def lifespan(app: FastAPI):
    # Startup
    await init_db()
    await init_cache()
    yield
    # Shutdown
    await close_db()
    await close_cache()

def create_app() -> FastAPI:
    app = FastAPI(
        title="ORGANVM Skills API",
        version="1.0.0",
        lifespan=lifespan,
    )
    app.include_router(skills_router, prefix="/api/skills", tags=["skills"])
    app.include_router(registry_router, prefix="/api/registry", tags=["registry"])
    app.add_middleware(CorrelationMiddleware)
    return app

app = create_app()
```

## Dependency Injection

```python
from fastapi import Depends
from typing import Annotated

async def get_db():
    async with async_session() as session:
        yield session

async def get_current_user(token: str = Depends(oauth2_scheme)) -> User:  # allow-secret
    user = await verify_token(token)
    if not user:
        raise HTTPException(status_code=401, detail="Invalid token")
    return user

# Type aliases for clean signatures
DB = Annotated[AsyncSession, Depends(get_db)]
CurrentUser = Annotated[User, Depends(get_current_user)]

@router.get("/skills/{skill_id}")
async def get_skill(skill_id: str, db: DB, user: CurrentUser) -> SkillResponse:
    skill = await db.get(Skill, skill_id)
    if not skill:
        raise HTTPException(status_code=404, detail="Skill not found")
    return SkillResponse.model_validate(skill)
```

## Pydantic Models

```python
from pydantic import BaseModel, Field
from datetime import datetime

class SkillBase(BaseModel):
    name: str = Field(pattern=r"^[a-z][a-z0-9-]*$", min_length=2, max_length=64)
    description: str = Field(min_length=20, max_length=600)
    category: str
    tags: list[str] = []

class SkillCreate(SkillBase):
    pass

class SkillResponse(SkillBase):
    id: str
    created_at: datetime
    updated_at: datetime

    model_config = {"from_attributes": True}

class SkillList(BaseModel):
    items: list[SkillResponse]
    total: int
    page: int
    per_page: int

From 4444J99/a-i--skills, MIT.

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