FastAPI 专家

精通异步 Python、Pydantic V2 和使用 FastAPI 进行生产级 API 开发。

何时使用此技能

• 使用 FastAPI 构建 REST API
• 实现 Pydantic V2 验证模式
• 设置异步数据库操作
• 实现 JWT 认证/授权
• 创建 WebSocket 端点
• 优化 API 性能

核心工作流

1. 分析需求 — 确定端点、数据模型、认证需求
2. 设计模式 — 创建 Pydantic V2 模型用于验证
3. 实现 — 编写带有正确依赖注入的异步端点
4. 安全 — 添加认证、授权、速率限制
5. 测试 — 使用 pytest 和 httpx 编写异步测试；每组端点完成后运行 pytest 并在 /docs 验证 OpenAPI 文档

每步之后检查点： 确认模式正确验证、端点返回预期的 HTTP 状态码、/docs 反映预期的 API 接口，然后再继续。

最小完整示例

模式 + 端点 + 依赖注入的完整单元：

# schemas.py
from pydantic import BaseModel, EmailStr, field_validator, model_config

class UserCreate(BaseModel):
    model_config = model_config(str_strip_whitespace=True)

    email: EmailStr
    password: str
    name: str | None = None

    @field_validator("password")
    @classmethod
    def password_strength(cls, v: str) -> str:
        if len(v) < 8:
            raise ValueError("Password must be at least 8 characters")
        return v

class UserResponse(BaseModel):
    model_config = model_config(from_attributes=True)

    id: int
    email: EmailStr
    name: str | None = None

# routers/users.py
from fastapi import APIRouter, Depends, HTTPException, status
from sqlalchemy.ext.asyncio import AsyncSession
from typing import Annotated

from app.database import get_db
from app.schemas import UserCreate, UserResponse
from app import crud

router = APIRouter(prefix="/users", tags=["users"])

DbDep = Annotated[AsyncSession, Depends(get_db)]

@router.post("/", response_model=UserResponse, status_code=status.HTTP_201_CREATED)
async def create_user(payload: UserCreate, db: DbDep) -> UserResponse:
    existing = await crud.get_user_by_email(db, payload.email)
    if existing:
        raise HTTPException(status_code=status.HTTP_409_CONFLICT, detail="Email already registered")
    return await crud.create_user(db, payload)

# crud.py
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession
from app.models import User
from app.schemas import UserCreate
from app.security import hash_password

async def get_user_by_email(db: AsyncSession, email: str) -> User | None:
    result = await db.execute(select(User).where(User.email == email))
    return result.scalar_one_or_none()

async def create_user(db: AsyncSession, payload: UserCreate) -> User:
    user = User(email=payload.email, hashed_password=hash_password(payload.password), name=payload.name)
    db.add(user)
    await db.commit()
    await db.refresh(user)
    return user

JWT 认证代码片段

# security.py
from datetime import datetime, timedelta, timezone
from jose import JWTError, jwt
from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from typing import Annotated

SECRET_KEY = "read-from-env"  # use os.environ / settings
ALGORITHM = "HS256"
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/auth/token")

def create_access_token(subject: str, expires_delta: timedelta = timedelta(minutes=30)) -> str:
    payload = {"sub": subject, "exp": datetime.now(timezone.utc) + expires_delta}
    return jwt.encode(payload, SECRET_KEY, algorithm=ALGORITHM)

async def get_current_user(token: Annotated[str, Depends(oauth2_scheme)]) -> str:
    try:
        data = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        subject: str | None = data.get("sub")
        if subject is None:
            raise ValueError
        return subject
    except (JWTError, ValueError):
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid credentials")

CurrentUser = Annotated[str, Depends(get_current_user)]

参考指南

根据上下文加载详细指导：

| 主题 | 参考文件 | 加载时机 | |------|----------|----------| | Pydantic V2 | references/pydantic-v2.md | 创建模式、验证、model_config | | SQLAlchemy | references/async-sqlalchemy.md | 异步数据库、模型、CRUD 操作 | | 端点 | references/endpoints-routing.md | APIRouter、依赖、路由 | | 认证 | references/authentication.md | JWT、OAuth2、get_current_user | | 测试 | references/testing-async.md | pytest-asyncio、httpx、fixtures | | Django 迁移 | references/migration-from-django.md | 从 Django/DRF 迁移到 FastAPI |

约束

必须做到

• 处处使用类型提示（FastAPI 要求）
• 使用 Pydantic V2 语法（field_validator、model_config 等）