callbacks=callback_router3.routes,
)

router2_override.include_router(router4_override)

router2_override.include_router(router4_default)

router2_default.include_router(
    router4_override,
    prefix="/level3",
    tags=["level3a", "level3b"],
    dependencies=[Depends(dep3)],
    responses={
        403: {"description": "Client error level 3"},
        503: {"description": "Server error level 3"},

@router_b.get("/")
def get_b():
    return {"msg": "B"}


@router_c.get("/")
def get_c():
    return {"msg": "C"}


router_b.include_router(router=router_c, prefix="/c")
router_a.include_router(router=router_b, prefix="/b")
app.include_router(router=router_a, prefix="/a")


client = TestClient(app)


@pytest.mark.parametrize(
    "path,expected_status,expected_response",
    [

def test_redirect_slashes_enabled():
    app = FastAPI()
    router = APIRouter()

    @router.get("/hello/")
    def hello_page() -> str:
        return "Hello, World!"

    app.include_router(router)

    client = TestClient(app)

    response = client.get("/hello/", follow_redirects=False)
    assert response.status_code == 200

    response = client.get("/hello", follow_redirects=False)

router = APIRouter()

sub_router = APIRouter()

app = FastAPI()


@sub_router.get("/")
def read_item():
    return {"id": "foo"}


router.include_router(sub_router, prefix="/items")

app.include_router(router)

client = TestClient(app)


def test_path_operation():
    response = client.get("/items/")
    assert response.status_code == 200, response.text

async def routerprefixindex(websocket: WebSocket, deps: DepList):
    await websocket.accept()
    await websocket.send_text(json.dumps(deps))
    await websocket.close()


app.include_router(router, dependencies=[create_dependency("router2")])
app.include_router(
    prefix_router, prefix="/prefix", dependencies=[create_dependency("prefix_router2")]
)


def test_index():
    client = TestClient(app)

    options:
        members:
            - openapi_version
            - webhooks
            - state
            - dependency_overrides
            - openapi
            - websocket
            - include_router
            - get
            - put
            - post
            - delete
            - options
            - head
            - patch
            - trace
            - on_event

async def router_ws_custom_error(websocket: WebSocket):
    raise CustomError()


def make_app(app=None, **kwargs):
    app = app or FastAPI(**kwargs)
    app.include_router(router)
    app.include_router(prefix_router, prefix="/prefix")
    app.include_router(native_prefix_route)
    return app


app = make_app(app)


def test_app():
    client = TestClient(app)

```

!!! info
    `users.router` contains the `APIRouter` inside of the file `app/routers/users.py`.

    And `items.router` contains the `APIRouter` inside of the file `app/routers/items.py`.

With `app.include_router()` we can add each `APIRouter` to the main `FastAPI` application.

It will include all the routes from that router as part of it.

!!! note "Technical Details"

## 多次使用不同的 `prefix` 包含同一个路由器

你也可以在*同一*路由器上使用不同的前缀来多次使用 `.include_router()`。

在有些场景这可能有用，例如以不同的前缀公开同一个的 API，比方说 `/api/v1` 和 `/api/latest`。

这是一个你可能并不真正需要的高级用法，但万一你有需要了就能够用上。

## 在另一个 `APIRouter` 中包含一个 `APIRouter`

与在 `FastAPI` 应用程序中包含 `APIRouter` 的方式相同，你也可以在另一个 `APIRouter` 中包含 `APIRouter`，通过：

```Python
router.include_router(other_router)
```

```Python hl_lines="26-27  30"
{!../../../docs_src/dependency_testing/tutorial001.py!}
```

!!! tip "提示"

    **FastAPI** 应用中的任何位置都可以实现覆盖依赖项。

    原依赖项可用于*路径操作函数*、*路径操作装饰器*（不需要返回值时）、`.include_router()` 调用等。

    FastAPI 可以覆盖这些位置的依赖项。

然后，使用 `app.dependency_overrides` 把覆盖依赖项重置为空**字典**：

```Python
app.dependency_overrides = {}
```

!!! tip "提示"