@asynccontextmanager
async def lifespan(app: FastAPI):
    items["foo"] = {"name": "Fighters"}
    items["bar"] = {"name": "Tenders"}
    yield
    # clean up items
    items.clear()


app = FastAPI(lifespan=lifespan)


@app.get("/items/{item_id}")
async def read_items(item_id: str):
    return items[item_id]


def test_read_items():
    # Before the lifespan starts, "items" is still empty

Weitere Informationen zu Starlettes `lifespan`-Handlern finden Sie in <a href="https://www.starlette.dev/lifespan/" class="external-link" target="_blank">Starlettes Lifespan-Dokumentation</a>.

Einschließlich, wie man Lifespan-Zustand handhabt, der in anderen Bereichen Ihres Codes verwendet werden kann.

///

## Unteranwendungen { #sub-applications }

# Testing Events: lifespan and startup - shutdown { #testing-events-lifespan-and-startup-shutdown }

When you need `lifespan` to run in your tests, you can use the `TestClient` with a `with` statement:

{* ../../docs_src/app_testing/tutorial004_py39.py hl[9:15,18,27:28,30:32,41:43] *}


You can read more details about the ["Running lifespan in tests in the official Starlette documentation site."](https://www.starlette.dev/lifespan/#running-lifespan-in-tests)

        yield {"sub_router": True}
        state.sub_router_shutdown = True

    sub_router = APIRouter(lifespan=subrouter_lifespan)

    router = APIRouter(lifespan=router_lifespan)
    router.include_router(sub_router)

    app = FastAPI(lifespan=lifespan)
    app.include_router(router)

    @app.get("/")
    def main(request: Request) -> dict[str, str]:
        assert request.state.app

/// info

You can read more about the Starlette `lifespan` handlers in <a href="https://www.starlette.dev/lifespan/" class="external-link" target="_blank">Starlette's  Lifespan' docs</a>.

Including how to handle lifespan state that can be used in other areas of your code.

///

## Sub Applications { #sub-applications }

Você pode ler mais sobre os manipuladores de `lifespan` do Starlette na <a href="https://www.starlette.dev/lifespan/" class="external-link" target="_blank">Documentação do Lifespan do Starlette</a>.

Incluindo como lidar com estado do lifespan que pode ser usado em outras áreas do seu código.

///

## Sub Aplicações { #sub-applications }

你可以在模块/文件的顶部加载它，但这也意味着即使你只是在运行一个简单的自动化测试，它也会**加载模型**，这样测试将**变慢**，因为它必须在能够独立运行代码的其他部分之前等待模型加载完成。

这就是我们要解决的问题——在处理请求前加载模型，但只是在应用开始接收请求前，而不是代码执行时。

## 生命周期 lifespan

你可以使用`FastAPI()`应用的`lifespan`参数和一个上下文管理器（稍后我将为你展示）来定义**启动**和**关闭**的逻辑。

让我们从一个例子开始，然后详细介绍。

我们使用`yield`创建了一个异步函数`lifespan()`像这样：

```Python hl_lines="16  19"
{!../../docs_src/events/tutorial003.py!}
```

    return x * 42


ml_models = {}


@asynccontextmanager
async def lifespan(app: FastAPI):
    # Load the ML model
    ml_models["answer_to_everything"] = fake_answer_to_everything_ml_model
    yield
    # Clean up the ML models and release the resources
    ml_models.clear()


app = FastAPI(lifespan=lifespan)


@app.get("/predict")
async def predict(x: float):

Если вам нужно, чтобы `lifespan` выполнялся в ваших тестах, вы можете использовать `TestClient` вместе с оператором `with`:

{* ../../docs_src/app_testing/tutorial004_py39.py hl[9:15,18,27:28,30:32,41:43] *}

Cuando necesitas que `lifespan` se ejecute en tus tests, puedes usar el `TestClient` con un statement `with`:

{* ../../docs_src/app_testing/tutorial004_py39.py hl[9:15,18,27:28,30:32,41:43] *}


Puedes leer más detalles sobre ["Ejecutar lifespan en tests en el sitio oficial de documentación de Starlette."](https://www.starlette.dev/lifespan/#running-lifespan-in-tests)