Es handelt sich also hier um eine Generatorfunktion, die die „generierende“ Arbeit intern auf etwas anderes überträgt.

    Auf diese Weise können wir das Ganze in einen `with`-Block einfügen und so sicherstellen, dass das dateiartige Objekt nach Abschluss geschlossen wird.

!!! tip "Tipp"

```

1. 这是第一阶段，称为`requirements-stage`。

2. 将 `/tmp` 设置为当前工作目录。

     这是我们生成文件`requirements.txt`的地方

3. 在此阶段安装Poetry。

4. 将`pyproject.toml`和`poetry.lock`文件复制到`/tmp`目录。

     因为它使用 `./poetry.lock*` （以 `*` 结尾），所以如果该文件尚不可用，它不会崩溃。

5. 生成`requirements.txt`文件。

6. 这是最后阶段，这里的任何内容都将保留在最终的容器镜像中。

7. 将当前工作目录设置为`/code`。

8. 将 `requirements.txt` 文件复制到 `/code` 目录。

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      </a>
    </div>
    <div class="item">

    Sie können `async`hrone oder reguläre Funktionen verwenden.

    **FastAPI** wird bei jeder das Richtige tun, so wie auch bei normalen Abhängigkeiten.

## Eine Abhängigkeit mit `yield` und `try`.

Wenn Sie einen `try`-Block in einer Abhängigkeit mit `yield` verwenden, empfangen Sie alle Exceptions, die bei Verwendung der Abhängigkeit geworfen wurden.

{!../../../docs_src/custom_response/tutorial008.py!}
```

1. This is the generator function. It's a "generator function" because it contains `yield` statements inside.
2. By using a `with` block, we make sure that the file-like object is closed after the generator function is done. So, after it finishes sending the response.

  "email": "******@****.***",
  "full_name": "John Doe",
  "disabled": false,
  "hashed_password": "fakehashedsecret"
}
```

<img src="/img/tutorial/security/image06.png">

If you click the lock icon and logout, and then try the same operation again, you will get an HTTP 401 error of:

```JSON
{
  "detail": "Not authenticated"
}
```

### Inactive user

### Path operation functions

When you declare a *path operation function* with normal `def` instead of `async def`, it is run in an external threadpool that is then awaited, instead of being called directly (as it would block the server).

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

When you create a context manager or an async context manager like above, what it does is that, before entering the `with` block, it will execute the code before the `yield`, and after exiting the `with` block, it will execute the code after the `yield`.

In our code example above, we don't use it directly, but we pass it to FastAPI for it to use it.

    {!> ../../../docs_src/sql_databases/sql_app/main.py!}
    ```

!!! info
    We put the creation of the `SessionLocal()` and handling of the requests in a `try` block.

    And then we close it in the `finally` block.

    This way we make sure the database session is always closed after the request. Even if there was an exception while processing the request.

```

!!! tip
    You can use `async` or regular functions.

    **FastAPI** will do the right thing with each, the same as with normal dependencies.

## A dependency with `yield` and `try`

If you use a `try` block in a dependency with `yield`, you'll receive any exception that was thrown when using the dependency.