We are importing the submodule `items` directly, instead of importing just its variable `router`.

This is because we also have another variable named `router` in the submodule `users`.

If we had imported one after the other, like:

```Python
from .routers.items import router
from .routers.users import router
```

        if responses is None:
            responses = {}
        for route in router.routes:
            if isinstance(route, APIRoute):
                combined_responses = {**responses, **route.responses}
                use_response_class = get_value_or_default(
                    route.response_class,
                    router.default_response_class,
                    default_response_class,

## Including Routers

When declaring routers, prefer to add router level parameters like prefix, tags, etc. to the router itself, instead of in `include_router()`.

Do this:

```python
from fastapi import APIRouter, FastAPI

app = FastAPI()

router = APIRouter(prefix="/items", tags=["items"])


@router.get("/")
async def list_items():
    return []

///

### Add the callback router { #add-the-callback-router }

At this point you have the *callback path operation(s)* needed (the one(s) that the *external developer*  should implement in the *external API*) in the callback router you created above.

Now use the parameter `callbacks` in *your API's path operation decorator* to pass the attribute `.routes` (that's actually just a `list` of routes/*path operations*) from that callback router:

## Custom `APIRoute` class in a router { #custom-apiroute-class-in-a-router }

You can also set the `route_class` parameter of an `APIRouter`:

{* ../../docs_src/custom_request_and_route/tutorial003_py310.py hl[26] *}

///

### 加入回呼 router { #add-the-callback-router }

此時你已經在先前建立的回呼 router 中，擁有所需的回呼「路徑操作（們）」（也就是「外部開發者」應該在「外部 API」中實作的那些）。

現在在「你的 API 的路徑操作裝飾器」中使用參數 `callbacks`，將該回呼 router 的屬性 `.routes`（實際上就是一個由路由／「路徑操作」所組成的 `list`）傳入：

{* ../../docs_src/openapi_callbacks/tutorial001_py310.py hl[33] *}

/// tip

///

### 避免名称冲突 { #avoid-name-collisions }

我们将直接导入 `items` 子模块，而不是仅导入其 `router` 变量。

这是因为我们在 `users` 子模块中也有另一个名为 `router` 的变量。

如果我们一个接一个地导入，例如：

```Python
from .routers.items import router
from .routers.users import router
```

来自 `users` 的 `router` 将覆盖来自 `items` 中的 `router`，我们将无法同时使用它们。

因此，为了能够在同一个文件中使用它们，我们直接导入子模块：

{* ../../docs_src/custom_request_and_route/tutorial002_an_py310.py hl[17:19] *}

## 라우터에서의 커스텀 `APIRoute` 클래스 { #custom-apiroute-class-in-a-router }

`APIRouter`의 `route_class` 파라미터를 설정할 수도 있습니다:

{* ../../docs_src/custom_request_and_route/tutorial003_py310.py hl[26] *}

이 예시에서는 `router` 아래의 *경로 처리*들이 커스텀 `TimedRoute` 클래스를 사용하며, 응답을 생성하는 데 걸린 시간을 담은 추가 `X-Response-Time` 헤더가 응답에 포함됩니다:

{* ../../docs_src/custom_request_and_route/tutorial002_an_py310.py hl[17:19] *}

## 在路由器中自訂 `APIRoute` 類別 { #custom-apiroute-class-in-a-router }

你也可以在 `APIRouter` 上設定 `route_class` 參數：

{* ../../docs_src/custom_request_and_route/tutorial003_py310.py hl[26] *}

在此範例中，`router` 底下的路徑操作會使用自訂的 `TimedRoute` 類別，並在回應中多加上一個 `X-Response-Time` 標頭，標示產生該回應所花費的時間：

## Features { #features }

- **Path Operation Explorer** - A sidebar tree view of all <dfn title="routes, endpoints">*path operations*</dfn> in your application. Click to jump to any route or router definition.
- **Route Search** - Search by path, method, or name with <kbd>Ctrl</kbd> + <kbd>Shift</kbd> + <kbd>E</kbd> (on macOS: <kbd>Cmd</kbd> + <kbd>Shift</kbd> + <kbd>E</kbd>).