| 参数 | 类型 | 描述 |
|------------|------|-------------|
| `title` | `str` | API 的标题。 |
| `summary` | `str` | API 的简短摘要。 <small>自 OpenAPI 3.1.0、FastAPI 0.99.0 起可用。.</small> |
| `description` | `str` | API 的简短描述。可以使用Markdown。 |
| `version` | `string` | API 的版本。这是您自己的应用程序的版本，而不是 OpenAPI 的版本。例如 `2.5.0` 。 |
| `terms_of_service` | `str` | API 服务条款的 URL。如果提供，则必须是 URL。 |

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):
        if not name.endswith("A"):
            raise ValueError("name must end in A")

app = FastAPI()


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


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


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


@app.post("/offers/")

    b: Annotated[float, Body(allow_inf_nan=False)] = 0,
) -> str:
    return "OK"


client = TestClient(app)


@pytest.mark.parametrize(
    "value,code",
    [
        ("-1", 200),
        ("inf", 200),
        ("-inf", 200),
        ("nan", 200),
        ("0", 200),
        ("342", 200),
    ],
)
def test_allow_inf_nan_param_true(value: str, code: int):
    response = client.post(f"/?x={value}")

    # TODO: In that case, define if File() should support example/examples too
    # @app.post("/form_example")
    # def form_example(firstname: str = Form(example="John")):
    #     return firstname

    # @app.post("/form_examples")
    # def form_examples(
    #     lastname: str = Form(
    #         ...,
    #         examples={
    #             "example1": {"summary": "last name summary", "value": "Doe"},

    * У запитах та відповідях буде представлений як `str`.
* `datetime.datetime`:
    * Пайтонівський `datetime.datetime`.
    * У запитах та відповідях буде представлений як `str` в форматі ISO 8601, як: `2008-09-15T15:53:00+05:00`.
* `datetime.date`:
    * Пайтонівський `datetime.date`.
    * У запитах та відповідях буде представлений як `str` в форматі ISO 8601, як: `2008-09-15`.
* `datetime.time`:

		}
	}
}

func TestParseKey(t *testing.T) {
	testCases := []struct {
		str         string
		expectedKey Key
	}{
		{
			str: "01894394-d046-4783-ba0d-f1c6885790dc.event",
			expectedKey: Key{
				Name:      "01894394-d046-4783-ba0d-f1c6885790dc",
				Extension: ".event",
				ItemCount: 1,
			},
		},
		{
			str: "100:01894394-d046-4783-ba0d-f1c6885790dc.event.snappy",
			expectedKey: Key{

```Python hl_lines="1  4"
{!../../docs_src/python_types/tutorial009.py!}
```

Wenn Sie `Optional[str]` anstelle von nur `str` verwenden, wird Ihr Editor Ihnen dabei helfen, Fehler zu erkennen, bei denen Sie annehmen könnten, dass ein Wert immer eine String (`str`) ist, obwohl er auch `None` sein könnte.

`Optional[Something]` ist tatsächlich eine Abkürzung für `Union[Something, None]`, diese beiden sind äquivalent.

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    host: str
    save_data: bool
    if_modified_since: str | None = None
    traceparent: str | None = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(headers: CommonHeaders = Header()):

    * In requests and responses will be represented as a `str`.
* `datetime.datetime`:
    * A Python `datetime.datetime`.
    * In requests and responses will be represented as a `str` in ISO 8601 format, like: `2008-09-15T15:53:00+05:00`.
* `datetime.date`:
    * Python `datetime.date`.
    * In requests and responses will be represented as a `str` in ISO 8601 format, like: `2008-09-15`.
* `datetime.time`: