* This is especially useful if you run `await myfile.read()` once and then need to read the contents again.
* `close()`: Closes the file.

As all these methods are `async` methods, you need to "await" them.

For example, inside of an `async` *path operation function* you can get the contents with:

```Python
contents = await myfile.read()
```

```Python
with open("file.txt") as file:
    file.read()
```

In neueren Versionen von Python gibt es auch einen **asynchronen Kontextmanager**. Sie würden ihn mit `async with` verwenden:

```Python
async with lifespan(app):
    await do_stuff()
```

8. Обратите внимание, что эта *функция-обработчик пути* использует обычный `def` вместо `async def`.

    Как и всегда в FastAPI, вы можете сочетать `def` и `async def` по необходимости.

    Если хотите освежить в памяти, когда что использовать, посмотрите раздел _"Нет времени?"_ в документации про [`async` и `await`](../async.md#in-a-hurry).

}


@app.get(
    "/items/{item_id}/name",
    response_model=Item,
    response_model_include=["name", "description"],
)
async def read_item_name(item_id: str):
    return items[item_id]


@app.get("/items/{item_id}/public", response_model=Item, response_model_exclude=["tax"])
async def read_item_public_data(item_id: str):

 * <http://www.apache.org/>.
 *
 */
package okhttp.regression.compare

import org.apache.hc.client5.http.async.methods.SimpleHttpRequests
import org.apache.hc.client5.http.async.methods.SimpleHttpResponse
import org.apache.hc.client5.http.impl.async.HttpAsyncClients
import org.apache.hc.core5.concurrent.FutureCallback
import org.apache.hc.core5.http.ProtocolVersion
import org.junit.Assert

///

### No async *path operation functions* { #non-async-path-operation-functions }

También puedes usar funciones `def` normales (sin `async`), y usar `yield` de la misma manera.

FastAPI se asegurará de ejecutarlo correctamente para que no bloquee el event loop.

Como en este caso la función no es async, el tipo de retorno correcto sería `Iterable[Item]`:

///

### Non-async *path operation functions* { #non-async-path-operation-functions }

You can also use regular `def` functions (without `async`), and use `yield` the same way.

FastAPI will make sure it's run correctly so that it doesn't block the event loop.

As in this case the function is not async, the right return type would be `Iterable[Item]`:

@app.get(
    "/response_model_has_default_factory_return_dict",
    response_model=ResponseModel,
)
async def response_model_has_default_factory_return_dict():
    return {"code": 200}


@app.get(
    "/response_model_has_default_factory_return_model",
    response_model=ResponseModel,
)
async def response_model_has_default_factory_return_model():
    return ResponseModel()


client = TestClient(app)

当你在**大型代码库**中，在**很多*路径操作***里反复使用**相同的依赖**时，这会特别有用。

## 要不要使用 `async`？ { #to-async-or-not-to-async }

由于依赖项也会由 **FastAPI** 调用（与*路径操作函数*相同），因此定义函数时同样的规则也适用。

你可以使用 `async def` 或普通的 `def`。

你可以在普通的 `def` *路径操作函数*中声明 `async def` 的依赖项；也可以在异步的 `async def` *路径操作函数*中声明普通的 `def` 依赖项，等等。

都没关系，**FastAPI** 知道该怎么处理。

/// note | 注意

如果不了解异步，请参阅文档中关于 `async` 和 `await` 的章节：[异步：*“着急了？”*](../../async.md#in-a-hurry)。

///

    tax: float | None = None
    tags: set[str] = set()


@app.post("/items/", tags=["items"])
async def create_item(item: Item) -> Item:
    return item


@app.get("/items/", tags=["items"])
async def read_items():
    return [{"name": "Foo", "price": 42}]


@app.get("/users/", tags=["users"])
async def read_users():