from typing import 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")
async def create_item(item: Item):
    """
    Create an item with all the information:

class ReviewNode(BaseModel):
    author: Author | None = None
    state: str


class Reviews(BaseModel):
    nodes: list[ReviewNode]


class PullRequestNode(BaseModel):
    number: int
    labels: Labels
    author: Author | None = None
    title: str
    createdAt: datetime
    lastEditedAt: datetime | None = None
    updatedAt: datetime | None = None
    state: str
    reviews: Reviews

Es erfordert eine etwas ausführlichere Konfiguration. Und da es auf WSGI (anstelle von ASGI) basiert, ist es nicht darauf ausgelegt, die hohe Leistung von Tools wie Uvicorn, Starlette und Sanic zu nutzen.

def test_raises_pydantic_v1_model_in_endpoint_param() -> None:
    class ParamModelV1(BaseModel):
        name: str

    app = FastAPI()

    with pytest.raises(PydanticV1NotSupportedError):

        @app.post("/param")
        def endpoint(data: ParamModelV1):  # pragma: no cover
            return data


def test_raises_pydantic_v1_model_in_return_type() -> None:
    class ReturnModelV1(BaseModel):
        name: str

    name: str
    price: Optional[float] = None
    owner_ids: Optional[list[int]] = None


@app.get("/items/invalid", response_model=Item)
def get_invalid():
    return {"name": "invalid", "price": "foo"}


@app.get("/items/invalidnone", response_model=Item)
def get_invalid_none():
    return None


@app.get("/items/validnone", response_model=Union[Item, None])
def get_valid_none(send_none: bool = False):

class Session:
    def __init__(self) -> None:
        self.data = ["foo", "bar", "baz"]
        self.open = True

    def __iter__(self) -> Generator[str, None, None]:
        for item in self.data:
            if self.open:
                yield item
            else:
                raise ValueError("Session closed")


@contextmanager
def acquire_session() -> Generator[Session, None, None]:
    session = Session()
    try:

from pydantic import BaseModel, Field

app = FastAPI()


class Item(BaseModel):
    name: str = Field(examples=["Foo"])
    description: Union[str, None] = Field(default=None, examples=["A very nice Item"])
    price: float = Field(examples=[35.4])
    tax: Union[float, None] = Field(default=None, examples=[3.2])


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

由于我们必须用 `Query(default=None)` 替换默认值 `None`，`Query` 的第一个参数同样也是用于定义默认值。

所以：

```Python
q: Union[str, None] = Query(default=None)
```

...使得参数可选，等同于：

```Python
q: str = None
```

但是 `Query` 显式地将其声明为查询参数。

然后，我们可以将更多的参数传递给 `Query`。在本例中，适用于字符串的 `max_length` 参数：

```Python
q: Union[str, None] = Query(default=None, max_length=50)
```

    Set<Feature<?>> features = copyToSet(getFeatures());
    @SuppressWarnings("rawtypes") // class literals
    List<Class<? extends AbstractTester>> testers = getTesters();

    logger.fine(" Testing: " + name);

    // Split out all the specified sizes.
    Set<Feature<?>> sizesToTest = Helpers.copyToSet(CollectionSize.values());
    sizesToTest.retainAll(features);
    features.removeAll(sizesToTest);

						<div class="d-sm-none"></div>
						<span class="d-none d-sm-inline-block">&nbsp;</span>
						<la:message key="labels.search_result_size"
							arg0="${fe:formatFileSize(doc.content_length)}" />
					</c:if>
					<c:if test="${searchLogSupport && doc.click_count!=null && doc.click_count>0}">
						<div class="d-sm-none"></div>
						<span class="d-none d-sm-inline-block">&nbsp;</span>