class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None


class User(BaseModel):
    username: str
    full_name: str | None = None


@app.put("/items/{item_id}")
async def update_item(
    item_id: int, item: Item, user: User, importance: Annotated[int, Body()]
):
    results = {"item_id": item_id, "item": item, "user": user, "importance": importance}

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


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

                    "name": "Foo",
                    "description": "A very nice Item",
                    "price": 35.4,
                    "tax": 3.2,
                }
            ]
        }


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

from pydantic import BaseModel

app = FastAPI()


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


@app.put("/items/{item_id}")
async def update_item(
    item_id: int,
    item: Annotated[
        Item,
        Body(
            examples=[
                {
                    "name": "Foo",

        }
        final Extractor extractor = extractorFactory.getExtractor(responseData.getMimeType());
        final Map<String, String> params = new HashMap<>();
        params.put(ExtractData.RESOURCE_NAME_KEY, getResourceName(responseData));
        params.put(ExtractData.CONTENT_TYPE, responseData.getMimeType());
        String content = null;
        try (final InputStream in = responseData.getResponseBody()) {

                        fieldMap.put("name", field.getName());
                        fieldMap.put("result", field.getValueCountMap().entrySet().stream().map(e -> {
                            final Map<String, Object> valueCount = new HashMap<>(2, 1f);
                            valueCount.put("value", e.getKey());
                            valueCount.put("count", e.getValue());

        public Map<String, String> extraInterpolationSource() {
            Map<String, String> extra = new HashMap<>();
            extra.put("session.topDirectory", topDirectory.toString());
            if (rootDirectory != null) {
                extra.put("session.rootDirectory", rootDirectory.toString());
            }
            return extra;
        }
    }

    @Override

                    if (queryMap == null) {
                        queryMap = new HashMap<>();
                        keyMatchQueryMap.put(virtualHost, queryMap);
                    }
                    final String termKey = toLowerCase(keyMatch.getTerm());

        default=None, title="The description of the item", max_length=300
    )
    price: float = Field(gt=0, description="The price must be greater than zero")
    tax: float | None = None


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

---

回到前面的代码示例，**FastAPI** 将会：

* 校验 `GET` 和 `PUT` 请求的路径中是否含有 `item_id`。
* 校验 `GET` 和 `PUT` 请求中的 `item_id` 是否为 `int` 类型。
    * 如果不是，客户端将会收到清晰有用的错误信息。
* 检查 `GET` 请求中是否有命名为 `q` 的可选查询参数（比如 `http://127.0.0.1:8000/items/foo?q=somequery`）。
    * 因为 `q` 被声明为 `= None`，所以它是可选的。
    * 如果没有 `None` 它将会是必需的 (如 `PUT` 例子中的请求体)。
* 对于访问 `/items/{item_id}` 的 `PUT` 请求，将请求体读取为 JSON 并：
    * 检查是否有必需属性 `name` 并且值为 `str` 类型 。