!!! note "Hinweis"
    FastAPI weiß nur dank des definierten Defaultwertes `=None`, dass der Wert von `q` nicht erforderlich ist

    `Union[str, None]` hingegen erlaubt ihren Editor, Sie besser zu unterstützen und Fehler zu erkennen.

## Zusätzliche Validierung

Wir werden bewirken, dass, obwohl `q` optional ist, wenn es gegeben ist, **seine Länge 50 Zeichen nicht überschreitet**.

  // RFC-6335 and https://www.iana.org/assignments/service-names).
  //
  // * Kubernetes-defined prefixed names:
  //   * 'kubernetes.io/h2c' - HTTP/2 over cleartext as described in https://www.rfc-editor.org/rfc/rfc7540
  //
  // * Other protocols should use implementation-defined prefixed names such as
  // mycompany.com/my-custom-protocol.
  // +optional
  optional string appProtocol = 4;
}

!!! tip
    Some editors check for unused function parameters, and show them as errors.

    Using these `dependencies` in the *path operation decorator* you can make sure they are executed while avoiding editor/tooling errors.

     * not be set within all security descriptors even though the ACE was in
     * face inherited. If an inherited ACE is added to a parent the Windows
     * ACL editor will rebuild all children ACEs and set this flag accordingly.
     */
    public boolean isInherited() {
        return (flags & FLAGS_INHERITED) != 0;
    }
    /**

     * @return the RID
     */
    int getRid ();


    /**
     * Return a String representing this SID ideal for display to
     * users. This method should return the same text that the ACL
     * editor in Windows would display.
     * <p>
     * Specifically, if the SID has
     * been resolved and it is not a domain SID or builtin account,
     * the full DOMAIN\name form of the account will be

And then, when using the dependency in a *path operation function*, we declare it with the type `Session` we imported directly from SQLAlchemy.

This will then give us better editor support inside the *path operation function*, because the editor will know that the `db` parameter is of type `Session`:

=== "Python 3.9+"

    ```Python hl_lines="22  30  36  45  51"
    {!> ../../../docs_src/sql_databases/sql_app_py39/main.py!}

```Python hl_lines="7"
{!../../../docs_src/path_params/tutorial002.py!}
```

En este caso, `item_id` es declarado como un `int`.

!!! check "Revisa"
    Esto te dará soporte en el editor dentro de tu función, con chequeo de errores, auto-completado, etc.

## <abbr title="también conocido en inglés como: serialization, parsing, marshalling">Conversión</abbr> de datos

...from:

```Python
        ... "item_name": item.name ...
```

...to:

```Python
        ... "item_price": item.price ...
```

...and see how your editor will auto-complete the attributes and know their types:

![editor support](https://fastapi.tiangolo.com/img/vscode-completion.png)

* <a href="https://code.visualstudio.com/" class="external-link" target="_blank">Visual Studio Code</a>에서:

![editor support](https://fastapi.tiangolo.com/img/vscode-completion.png)

* <a href="https://www.jetbrains.com/pycharm/" class="external-link" target="_blank">PyCharm</a>에서:

![editor support](https://fastapi.tiangolo.com/img/pycharm-completion.png)

Up to now, you have been using common data types, like:

* `int`
* `float`
* `str`
* `bool`

But you can also use more complex data types.

And you will still have the same features as seen up to now:

* Great editor support.
* Data conversion from incoming requests.
* Data conversion for response data.
* Data validation.
* Automatic annotation and documentation.

## Other data types