As always, in FastAPI you can combine `def` and `async def` as needed.

    If you need a refresher about when to use which, check out the section _"In a hurry?"_ in the docs about [`async` and `await`](../async.md#in-a-hurry){.internal-link target=_blank}.

And then you also read how to handle [CORS with the `CORSMiddleware`](../tutorial/cors.md){.internal-link target=_blank}.

In this section we'll see how to use other middlewares.

## Adding ASGI middlewares { #adding-asgi-middlewares }

# Tutoriel - Guide utilisateur - Introduction

Ce tutoriel vous montre comment utiliser **FastAPI** avec la plupart de ses fonctionnalités, étape par étape.

Chaque section s'appuie progressivement sur les précédentes, mais elle est structurée de manière à séparer les sujets, afin que vous puissiez aller directement à l'un d'entre eux pour résoudre vos besoins spécifiques en matière d'API.

Il est également conçu pour fonctionner comme une référence future.

# Замеры производительности

Независимые тесты производительности приложений от TechEmpower показывают, что **FastAPI** под управлением Uvicorn <a href="https://www.techempower.com/benchmarks/#section=test&runid=7464e520-0dc2-473d-bd34-dbdfd7e85911&hw=ph&test=query&l=zijzen-7" class="external-link" target="_blank">один из самых быстрых Python-фреймворков</a> и уступает только Starlette и Uvicorn (которые используются в FastAPI). (*)

Since before **JSON Schema** supported `examples` OpenAPI had support for a different field also called `examples`.

This **OpenAPI-specific** `examples` goes in another section in the OpenAPI specification. It goes in the **details for each *path operation***, not inside each JSON Schema.

      type: String?,
      data: String,
    )

    fun onRetryChange(timeMs: Long)
  }

  /**
   * Process the next event. This will result in a single call to [Callback.onEvent] *unless* the
   * data section was empty. Any number of calls to [Callback.onRetryChange] may occur while
   * processing an event.
   *
   * @return false when EOF is reached
   */
  @Throws(IOException::class)
  fun processNextEvent(): Boolean {

# Benchmarks

Los benchmarks independientes de TechEmpower muestran aplicaciones de **FastAPI** ejecutándose bajo Uvicorn como <a href="https://www.techempower.com/benchmarks/#section=test&runid=7464e520-0dc2-473d-bd34-dbdfd7e85911&hw=ph&test=query&l=zijzen-7" class="external-link" target="_blank">uno de los frameworks de Python más rápidos disponibles</a>, solo por debajo de Starlette y Uvicorn en sí mismos (utilizados internamente por FastAPI).

### Template `url_for` Arguments { #template-url-for-arguments }

You can also use `url_for()` inside of the template, it takes as arguments the same arguments that would be used by your *path operation function*.

So, the section with:

{% raw %}

```jinja
<a href="{{ url_for('read_item', id=id) }}">
```

{% endraw %}

    public static Artifact copyArtifact(Artifact artifact) {
        VersionRange range = artifact.getVersionRange();

        // For some reason with the introduction of MNG-1577 we have the case in Yoko where a depMan section has
        // something like the following:
        //
        // <dependencyManagement>
        //     <dependencies>
        //         <!--  Yoko modules -->
        //         <dependency>

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.

If you are just starting with **FastAPI** you might want to skip this section.

///

## Use cases { #use-cases }

Some use cases include:

* Converting non-JSON request bodies to JSON (e.g. <a href="https://msgpack.org/index.html" class="external-link" target="_blank">`msgpack`</a>).