```html
Item ID: 42
```

### 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 %}

# 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). (*)

{!../../docs_src/websockets/tutorial002.py!}
```

/// info

👉 *️⃣ ⚫️ 🚫 🤙 ⚒ 🔑 🤚 `HTTPException`, ↩️ 👥 🤚 `WebSocketException`.

👆 💪 ⚙️ 📪 📟 ⚪️➡️ <a href="https://tools.ietf.org/html/rfc6455#section-7.4.1" class="external-link" target="_blank">☑ 📟 🔬 🔧</a>.

///

### 🔄 *️⃣ ⏮️ 🔗

🚥 👆 📁 📛 `main.py`, 🏃 👆 🈸 ⏮️:

<div class="termy">

```console
$ uvicorn main:app --reload

# Fess: エンタープライズ検索サーバー
[![Java CI with Maven](https://github.com/codelibs/fess/actions/workflows/maven.yml/badge.svg)](https://github.com/codelibs/fess/actions/workflows/maven.yml)
[![Maven Central](https://maven-badges.herokuapp.com/maven-central/org.codelibs.fess/fess/badge.svg)](https://maven-badges.herokuapp.com/maven-central/org.codelibs.fess/fess)

</p>
<p align="center">
    FastAPI framework, zeer goede prestaties, eenvoudig te leren, snel te programmeren, klaar voor productie
</p>
<p align="center">
<a href="https://github.com/fastapi/fastapi/actions?query=workflow%3ATest+event%3Apush+branch%3Amaster" target="_blank">
    <img src="https://github.com/fastapi/fastapi/workflows/Test/badge.svg?event=push&branch=master" alt="Test">
</a>

# 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.

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

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>).

   * typically useful for {@code return} statements. That leaves the code with two options: Either
   * add the suppression to the whole method (which turns off checking for a large section of code),
   * or extract a variable, and put the suppression on that. However, a local variable typically
   * doesn't work: Because nullness analyses typically infer the nullness of local variables,

     * 
     */
    public static final int FILE_NOTIFY_CHANGE_STREAM_SIZE = 0x00000400;

    /**
     * 
     */
    public static final int FILE_NOTIFY_CHANGE_STREAM_WRITE = 0x00000800;

    // actions returned
    /**
     * File has been added
     */
    public static final int FILE_ACTION_ADDED = 0x00000001;
    /**
     * File has been removed
     */

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