operation ->> client: Return response to client
    Note over client,operation: Response is already sent, can't change it anymore
    opt Tasks
        operation -->> tasks: Send background tasks
    end
    opt Raise other exception
        tasks -->> tasks: Handle exceptions in the background task code
    end
```

!!! info

```Python hl_lines="6-9"
{!../../../docs_src/background_tasks/tutorial001.py!}
```

## 🚮 🖥 📋

🔘 👆 *➡ 🛠️ 🔢*, 🚶‍♀️ 👆 📋 🔢 *🖥 📋* 🎚 ⏮️ 👩‍🔬 `.add_task()`:

```Python hl_lines="14"
{!../../../docs_src/background_tasks/tutorial001.py!}
```

`.add_task()` 📨 ❌:

* 📋 🔢 🏃 🖥 (`write_notification`).
* 🙆 🔁 ❌ 👈 🔜 🚶‍♀️ 📋 🔢 ✔ (`email`).

        content = f"notification for {email}: {message}"
        email_file.write(content)


@app.post("/send-notification/{email}")
async def send_notification(email: str, background_tasks: BackgroundTasks):
    background_tasks.add_task(write_notification, email, message="some notification")

!!! tip

* There can be **multiple processes** of the **same program** running at the same time.

If you check out the "task manager" or "system monitor" (or similar tools) in your operating system, you will be able to see many of those processes running.

Starlette und **FastAPI** basieren auf <a href="https://anyio.readthedocs.io/en/stable/" class="external-link" target="_blank">AnyIO</a>, welches diese sowohl mit der Python-Standardbibliothek <a href="https://docs.python.org/3/library/asyncio-task.html" class="external-link" target="_blank">asyncio</a>, als auch mit <a href="https://trio.readthedocs.io/en/stable/" class="external-link" target="_blank">Trio</a> kompatibel macht.

    raise OtherDependencyError()


@app.get("/context_b_bg")
async def get_context_b_bg(tasks: BackgroundTasks, state: dict = Depends(context_b)):
    async def bg(state: dict):
        state["bg"] = f"bg set - b: {state['context_b']} - a: {state['context_a']}"

    tasks.add_task(bg, state)
    return state


# Sync versions


@app.get("/sync_async")

Mas se você quiser usar `async` / `await` sem FastAPI, <a href="https://docs.python.org/3/library/asyncio-task.html#coroutine" class="external-link" target="_blank">verifique a documentação oficial Python</a>.

### Outras formas de código assíncrono

Esse estilo de usar `async` e `await` é relativamente novo na linguagem.

Mais si vous utilisez `async` / `await` sans **FastAPI**, <a href="https://docs.python.org/3/library/asyncio-task.html#coroutine" class="external-link" target="_blank">allez jetez un coup d'oeil à la documentation officielle de Python</a>.

### Autres formes de code asynchrone

Starlette и **FastAPI** основаны на <a href="https://anyio.readthedocs.io/en/stable/" class="external-link" target="_blank">AnyIO</a>, которая делает их совместимыми как с <a href="https://docs.python.org/3/library/asyncio-task.html" class="external-link" target="_blank">asyncio</a> - стандартной библиотекой Python, так и с <a href="https://trio.readthedocs.io/en/stable/" class="external-link" target="_blank">Trio</a>.