fastapi

FastAPI Best Practices

Overview

Aspect	Recommendation
Validation	Pydantic v2
Database	SQLAlchemy 2.0 async or asyncpg
Auth	OAuth2 with JWT
Docs	Auto-generated OpenAPI

---

Project Structure

app/
├── main.py              # FastAPI application
├── config.py            # Settings
├── database.py          # Database connection
├── dependencies.py      # Shared dependencies
├── models/              # SQLAlchemy models
│   ├── __init__.py
│   └── user.py
├── schemas/             # Pydantic schemas
│   ├── __init__.py
│   └── user.py
├── routers/             # API routes
│   ├── __init__.py
│   └── users.py
├── services/            # Business logic
│   └── user_service.py
└── utils/
    └── security.py

---

Application Setup

Main Application

# app/main.py
from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware
from contextlib import asynccontextmanager

from app.routers import users, posts
from app.database import init_db

@asynccontextmanager
async def lifespan(app: FastAPI):
    # Startup
    await init_db()
    yield
    # Shutdown
    # cleanup here

app = FastAPI(
    title="My API",
    version="1.0.0",
    lifespan=lifespan,
)

app.add_middleware(
    CORSMiddleware,
    allow_origins=["http://localhost:3000"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

app.include_router(users.router, prefix="/api/users", tags=["users"])
app.include_router(posts.router, prefix="/api/posts", tags=["posts"])

Configuration

# app/config.py
from pydantic_settings import BaseSettings
from functools import lru_cache

class Settings(BaseSettings):
    database_url: str
    secret_key: str
    algorithm: str = "HS256"
    access_token_expire_minutes: int = 30
    
    model_config = {"env_file": ".env"}

@lru_cache
def get_settings() -> Settings:
    return Settings()

---

Pydantic Schemas

Request/Response Models