fastapi-guide

Guide FastAPI

Workflow

1. Bootstrapper le projet

pip install "fastapi[standard]" sqlalchemy[asyncio] alembic pydantic-settings httpx pytest pytest-asyncio

Structure recommandée :

app/
  main.py          # lifespan, include_router, middleware
  config.py        # Settings via pydantic-settings
  dependencies.py  # Depends() partagés (db, auth, pagination)
  routers/
    users.py
    items.py
  schemas/
    user.py        # UserCreate, UserUpdate, UserResponse
  models/
    user.py        # SQLAlchemy ORM
  services/
    user_service.py
  repositories/
    user_repo.py
tests/
  conftest.py      # fixtures DB, client async
  test_users.py

2. Config typée avec pydantic-settings

# app/config.py
from pydantic_settings import BaseSettings

class Settings(BaseSettings):
    database_url: str
    secret_key: str
    debug: bool = False
    cors_origins: list[str] = []

    model_config = {"env_file": ".env"}

settings = Settings()

3. Schémas Pydantic v2 — séparer Create / Update / Response

# app/schemas/user.py
from pydantic import BaseModel, EmailStr, Field
from datetime import datetime

class UserCreate(BaseModel):
    email: EmailStr
    password: str = Field(min_length=8)
    username: str = Field(max_length=50)

class UserUpdate(BaseModel):
    username: str | None = Field(None, max_length=50)

class UserResponse(BaseModel):
    id: int
    email: EmailStr
    username: str
    created_at: datetime

    model_config = {"from_attributes": True}

Règle : jamais réutiliser UserCreate comme response_model — le schéma de réponse ne doit pas contenir le mot de passe.

4. Lifespan + application factory

# app/main.py
from contextlib import asynccontextmanager
from fastapi import FastAPI
from app.routers import users, items

@asynccontextmanager
async def lifespan(app: FastAPI):
    # startup
    yield
    # shutdown

def create_app() -> FastAPI:
    app = FastAPI(
        title="Mon API",
        lifespan=lifespan,
        docs_url="/docs" if settings.debug else None,
    )
    app.include_router(users.router, prefix="/users", tags=["users"])
    app.include_router(items.router, prefix="/items", tags=["items"])
    return app

app = create_app()