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})

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: list[str] = Query(default=["foo", "bar"])):
    query_items = {"q": q}

from fastapi import FastAPI, Query

app = FastAPI()


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

    assert response.json() == {"detail": "Incorrect username or password"}


@needs_py310
def test_login_incorrect_username(client: TestClient):
    response = client.post("/token", data={"username": "foo", "password": "secret"})
    assert response.status_code == 400, response.text
    assert response.json() == {"detail": "Incorrect username or password"}


@needs_py310
def test_no_token(client: TestClient):

    assert response.json() == {"detail": "Incorrect username or password"}


@needs_py39
def test_login_incorrect_username(client: TestClient):
    response = client.post("/token", data={"username": "foo", "password": "secret"})
    assert response.status_code == 400, response.text
    assert response.json() == {"detail": "Incorrect username or password"}


@needs_py39
def test_no_token(client: TestClient):