In einigen Fällen möchten Sie möglicherweise die von den Klassen `Request` und `APIRoute` verwendete Logik überschreiben.

Das kann insbesondere eine gute Alternative zur Logik in einer Middleware sein.

Wenn Sie beispielsweise den <abbr title="Anfragekörper">Requestbody</abbr> lesen oder manipulieren möchten, bevor er von Ihrer Anwendung verarbeitet wird.

/// danger | Gefahr

   * interned, and so does not prevent these instances from being garbage-collected. This most
   * likely does not perform as well as {@link #newStrongInterner}, but is the best alternative when
   * the memory usage of that implementation is unacceptable.
   */
  @GwtIncompatible("java.lang.ref.WeakReference")
  public static <E> Interner<E> newWeakInterner() {
    return newBuilder().weak().build();

⚠️ **ATTENTION** ⚠️

Si vous démarrez un nouveau projet de zéro, allez voir les alternatives au début de cette page.

Par exemple, le générateur de projet <a href="https://github.com/tiangolo/full-stack-fastapi-postgresql" class="external-link" target="_blank">Full Stack FastAPI PostgreSQL</a>  peut être une meilleure alternative, étant activement maintenu et utilisé et comprenant toutes les nouvelles fonctionnalités et améliorations.

```

////

//// tab | Python 3.9+

```Python hl_lines="1  4"
{!> ../../docs_src/python_types/tutorial009_py39.py!}
```

////

//// tab | Python 3.9+ Alternative

```Python hl_lines="1  4"
{!> ../../docs_src/python_types/tutorial009b_py39.py!}
```

////

#### `Union` oder `Optional` verwenden? { #using-union-or-optional }

* Show a **clear error** for the client when the data is not valid
* **Document** the parameter in the OpenAPI schema *path operation* (so it will show up in the **automatic docs UI**)

## Alternative (old): `Query` as the default value { #alternative-old-query-as-the-default-value }

# Custom Request and APIRoute class { #custom-request-and-apiroute-class }

In some cases, you may want to override the logic used by the `Request` and `APIRoute` classes.

In particular, this may be a good alternative to logic in a middleware.

For example, if you want to read or manipulate the request body before it is processed by your application.

/// danger

This is an "advanced" feature.

{* ../../docs_src/events/tutorial003_py39.py hl[22] *}

## Eventos alternativos (descontinuados) { #alternative-events-deprecated }

/// warning | Atenção

    checkHelperVersion(getClass().getClassLoader(), "SafeAtomicHelper");
    checkHelperVersion(NO_ATOMIC_FIELD_UPDATER, "SynchronizedAtomicHelper");

    // Then, run the actual tests under each alternative classloader:

    runTestMethod(NO_ATOMIC_FIELD_UPDATER);
    // TODO(lukes): assert that the logs are full of errors
  }

  /**

   * interned, and so does not prevent these instances from being garbage-collected. This most
   * likely does not perform as well as {@link #newStrongInterner}, but is the best alternative when
   * the memory usage of that implementation is unacceptable.
   */
  @GwtIncompatible("java.lang.ref.WeakReference")
  public static <E> Interner<E> newWeakInterner() {
    return newBuilder().weak().build();

Sie wird direkt in FastAPI importiert/inkludiert, sodass Sie sie von `fastapi` importieren können und vermeiden, versehentlich das alternative `BackgroundTask` (ohne das `s` am Ende) von `starlette.background` zu importieren.