This will be especially useful when you use it in a **large code base** where you use **the same dependencies** over and over again in **many *path operations***.

## To `async` or not to `async`

As dependencies will also be called by **FastAPI** (the same as your *path operation functions*), the same rules apply while defining your functions.

    ```

    </div>

=== "Hypercorn"

    <div class="termy">

    ```console
    $ hypercorn main:app --bind 0.0.0.0:80

    Running on 0.0.0.0:8080 over http (CTRL + C to quit)
    ```

    </div>

!!! warning "Achtung"
    Denken Sie daran, die Option `--reload` zu entfernen, wenn Sie diese verwendet haben.

=== "Python 3.8+"

    ```Python hl_lines="20-21"
    {!> ../../../docs_src/path_operation_configuration/tutorial003.py!}
    ```

## Description from docstring

    !!! tip
        Prefer to use the `Annotated` version if possible.

    ```Python hl_lines="12"
    {!> ../../../docs_src/request_files/tutorial001.py!}
    ```

Using `UploadFile` has several advantages over `bytes`:

* You don't have to use `File()` in the default value of the parameter.
* It uses a "spooled" file:
    * A file stored in memory up to a maximum size limit, and after passing this limit it will be stored in disk.

participant dep as Abhängigkeit mit yield
participant operation as Pfadoperation
participant tasks as Hintergrundtasks

    Note over client,operation: Kann Exceptions auslösen, inklusive HTTPException
    client ->> dep: Startet den Request
    Note over dep: Führt den Code bis zum yield aus
    opt Löst Exception aus
        dep -->> handler: Löst Exception aus
        handler -->> client: HTTP-Error-Response

{!../../../docs_src/custom_response/tutorial007.py!}
```

#### Using `StreamingResponse` with file-like objects

If you have a file-like object (e.g. the object returned by `open()`), you can create a generator function to iterate over that file-like object.

That way, you don't have to read it all first in memory, and you can pass that generator function to the `StreamingResponse`, and return it.

    ```

    </div>

=== "Hypercorn"

    <div class="termy">

    ```console
    $ hypercorn main:app --bind 0.0.0.0:80

    Running on 0.0.0.0:8080 over http (CTRL + C to quit)
    ```

    </div>

!!! warning "Предупреждение"

    Не забудьте удалить опцию `--reload`, если ранее пользовались ею.

    ```

    </div>


=== "Hypercorn"

    <div class="termy">

    ```console
    $ hypercorn main:app --bind 0.0.0.0:80

    Running on 0.0.0.0:8080 over http (CTRL + C to quit)
    ```

    </div>

!!! warning
     如果您正在使用`--reload`选项，请记住删除它。

     `--reload` 选项消耗更多资源，并且更不稳定。

     它在**开发**期间有很大帮助，但您**不应该**在**生产环境**中使用它。

## Hypercorn with Trio

---

"_I’m over the moon excited about **FastAPI**. It’s so fun!_"

try:
    import email_validator

    assert email_validator  # make autoflake ignore the unused import
    from pydantic import EmailStr
except ImportError:  # pragma: no cover

    class EmailStr(str):  # type: ignore
        @classmethod
        def __get_validators__(cls) -> Iterable[Callable[..., Any]]:
            yield cls.validate

        @classmethod