from typing import Optional

from fastapi import Depends, FastAPI
from pydantic import BaseModel, validator

app = FastAPI()


class ModelB(BaseModel):
    username: str


class ModelC(ModelB):
    password: str


class ModelA(BaseModel):
    name: str
    description: Optional[str] = None
    model_b: ModelB

    @validator("name")
    def lower_username(cls, name: str, values):

    "size": "XL"
  }
}

```

### FastAPI `HTTPException` vs Starlette `HTTPException`

**FastAPI** 也提供了自有的 `HTTPException`。

**FastAPI** 的 `HTTPException` 继承自 Starlette 的 `HTTPException` 错误类。

它们之间的唯一区别是，**FastAPI** 的 `HTTPException` 可以在响应中添加响应头。

OAuth 2.0 等安全工具需要在内部调用这些响应头。

因此你可以继续像平常一样在代码中触发 **FastAPI** 的 `HTTPException` 。

但注册异常处理器时，应该注册到来自 Starlette 的 `HTTPException`。

        ("/items", {"X-Header": "notvalid"}, 200, {"strange_header": None}),
        (
            "/items",
            {"strange_header": "FastAPI test"},
            200,
            {"strange_header": "FastAPI test"},
        ),
        (
            "/items",
            {"strange-header": "Not really underscore"},
            200,
            {"strange_header": None},
        ),
    ],
)

from typing import Union

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(
    q: Union[str, None] = Query(
        default=None,
        alias="item-query",
        title="Query string",
        description="Query string for the items to search in the database that have a good match",
        min_length=3,
        max_length=50,
        pattern="^fixedquery$",
        deprecated=True,

from fastapi import Depends, FastAPI, Header, HTTPException

app = FastAPI()


async def verify_token(x_token: str = Header()):
    if x_token != "fake-super-secret-token":
        raise HTTPException(status_code=400, detail="X-Token header invalid")


async def verify_key(x_key: str = Header()):
    if x_key != "fake-super-secret-key":
        raise HTTPException(status_code=400, detail="X-Key header invalid")
    return x_key

from typing import Set, Union

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: Union[str, None] = None
    price: float
    tax: Union[float, None] = None
    tags: Set[str] = set()


@app.post(
    "/items/",
    response_model=Item,
    summary="Create an item",

from typing import List, Set, Union

from fastapi import FastAPI
from pydantic import BaseModel, HttpUrl

app = FastAPI()


class Image(BaseModel):
    url: HttpUrl
    name: str


class Item(BaseModel):
    name: str
    description: Union[str, None] = None
    price: float
    tax: Union[float, None] = None
    tags: Set[str] = set()
    images: Union[List[Image], None] = None


@app.put("/items/{item_id}")

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None
    tags: list = []


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item):
    results = {"item_id": item_id, "item": item}

from typing import Union

from fastapi import Cookie, FastAPI
from pydantic import BaseModel

app = FastAPI()


class Cookies(BaseModel):
    model_config = {"extra": "forbid"}

    session_id: str
    fatebook_tracker: Union[str, None] = None
    googall_tracker: Union[str, None] = None


@app.get("/items/")
async def read_items(cookies: Cookies = Cookie()):

        run: |
          cd dist
          tar xvf fastapi*.tar.gz
      - name: Install test dependencies
        run: |
          cd dist/fastapi*/
          pip install -r requirements-tests.txt
        env:
          TIANGOLO_BUILD_PACKAGE: ${{ matrix.package }}
      - name: Run source distribution tests
        run: |
          cd dist/fastapi*/
          bash scripts/test.sh
      - name: Build wheel distribution