```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.

1️⃣. 👉 🥇 ▶️, ⚫️ 🌟 `requirements-stage`.

2️⃣. ⚒ `/tmp` ⏮️ 👷 📁.

    📥 🌐❔ 👥 🔜 🏗 📁 `requirements.txt`

3️⃣. ❎ 🎶 👉 ☁ ▶️.

4️⃣. 📁 `pyproject.toml` & `poetry.lock` 📁 `/tmp` 📁.

    ↩️ ⚫️ ⚙️ `./poetry.lock*` (▶️ ⏮️ `*`), ⚫️ 🏆 🚫 💥 🚥 👈 📁 🚫 💪.

5️⃣. 🏗 `requirements.txt` 📁.

6️⃣. 👉 🏁 ▶️, 🕳 📥 🔜 🛡 🏁 📦 🖼.

7️⃣. ⚒ ⏮️ 👷 📁 `/code`.

```

1. これは最初のステージで、`requirements-stage`と名付けられます
2. `/tmp` を現在の作業ディレクトリに設定します
    ここで `requirements.txt` というファイルを生成します。

3. このDockerステージにPoetryをインストールします

4. pyproject.toml`と`poetry.lock`ファイルを`/tmp` ディレクトリにコピーします

    `./poetry.lock*`（末尾に`*`）を使用するため、そのファイルがまだ利用できない場合でもクラッシュすることはないです。
5. requirements.txt`ファイルを生成します

6. これは最後のステージであり、ここにあるものはすべて最終的なコンテナ・イメージに保存されます
7. 現在の作業ディレクトリを `/code` に設定します

        <span class="sponsor-badge">sponsor</span>
        <img class="sponsor-image" src="/img/sponsors/cryptapi-banner.svg" />
      </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).