price: float
    tax: Union[float, None] = None


@app.put("/items/{item_id}")
async def update_item(
    item_id: int,
    item: Item = Body(
        examples=[
            {
                "name": "Foo",
                "description": "A very nice Item",
                "price": 35.4,
                "tax": 3.2,
            }
        ],
    ),
):
    results = {"item_id": item_id, "item": item}

from fastapi import FastAPI

app = FastAPI()


@app.get("/keyword-weights/", response_model=dict[str, float])
async def read_keyword_weights():

foo iRFmWghs3CK9/2HSvRja4TzX8HsRwzbVY+h0HRkH9uPho2BGmrG5a0/+rkLSA3GUOX/WiPmP+h73T1r0DZIDJXtOgYWIU/y2H+WAe/ZlWt90N2KHka0bkXajoE/3mu7jiCW45hTNBDp3ArJ+K8Oh6bEfN2bHhXjZ41Zk+uvksVba2ZNyhThAAGZgi/pRa/oCT4HUoBWcY3w96+TGR6uXtvbDOM9WhPXGo+1bwhAsA/RXPA1ZX+oS6t4rl/ZvkMZZN4VO5OvKph8tth/BGEK6mw4oTRa1Hd91+bUUqQh6hl3JeDk/t2KDWOEehOxgOqfVG72U/pUXrcUXuywq9KT+bWQxdJsXzwkkyT8Ovz4o/Ib8Xxz+BHwpN3TtOXsHziuqLGMz+OxetaxhQqe1G/UWwfi5a9PuJC3wfITSa0=...

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(
    q: Annotated[Union[str, None], Query(min_length=3, max_length=50)] = None,
):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

app = FastAPI()


@app.get("/items/")
async def read_items(
    q: Annotated[
        str | None, Query(min_length=3, max_length=50, regex="^fixedquery$")
    ] = None,
):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

```Python hl_lines="11"
{!../../docs_src/handling_errors/tutorial001.py!}

```

### 响应结果

请求为 `http://example.com/items/foo`（`item_id` 为 `「foo」`）时，客户端会接收到 HTTP 状态码 - 200 及如下 JSON 响应结果：

```JSON
{
  "item": "The Foo Wrestlers"
}

```

但如果客户端请求 `http://example.com/items/bar`（`item_id` `「bar」` 不存在时），则会接收到 HTTP 状态码 - 404（「未找到」错误）及如下 JSON 响应结果：

```JSON
{

                </div>
            </la:form>

        </section>
    </div>
    <jsp:include page="/WEB-INF/view/common/admin/footer.jsp"></jsp:include>
</div>
<jsp:include page="/WEB-INF/view/common/admin/foot.jsp"></jsp:include>
</body>

                </div>
            </div>
        </section>
    </div>
    <jsp:include page="/WEB-INF/view/common/admin/footer.jsp"></jsp:include>
</div>
<jsp:include page="/WEB-INF/view/common/admin/foot.jsp"></jsp:include>
</body>

                </div>
            </la:form>
        </section>
    </div>
    <jsp:include page="/WEB-INF/view/common/admin/footer.jsp"></jsp:include>
</div>
<jsp:include page="/WEB-INF/view/common/admin/foot.jsp"></jsp:include>
</body>

app = FastAPI()


@app.get("/items/")
async def read_items(
    q: Annotated[Union[str, None], Query(title="Query string", min_length=3)] = None,
):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})