is not available, instead of erroring out, the dependency result will
                be `None`.

                This is useful when you want to have optional authentication.

                It is also useful when you want to have authentication that can be
                provided in one of multiple optional ways (for example, with OAuth2
                or in a cookie).
                """

                is not available, instead of erroring out, the dependency result will
                be `None`.

                This is useful when you want to have optional authentication.

                It is also useful when you want to have authentication that can be
                provided in one of multiple optional ways (for example, in HTTP Basic
                authentication or in an HTTP Bearer token).

    * This is particularly important for **security**, we'll see more of that below.

## `response_model` Parameter

There are some cases where you need or want to return some data that is not exactly what the type declares.

And it shows their true commitment to FastAPI and its **community** (you), as they not only want to provide you a **good service** but also want to make sure you have a **good and healthy framework**, FastAPI. 🙇

For example, you might want to try <a href="https://speakeasyapi.dev/?utm_source=fastapi+repo&utm_medium=github+sponsorship" class="external-link" target="_blank">Speakeasy</a>.

By default, **FastAPI** will create a `server` in the OpenAPI schema with the URL for the `root_path`.

But you can also provide other alternative `servers`, for example if you want *the same* docs UI to interact with a staging and production environments.

```JSON
{"item_id":3}
```

!!! check "vérifier"
    Comme vous l'avez remarqué, la valeur reçue par la fonction (et renvoyée ensuite) est `3`,
    en tant qu'entier (`int`) Python, pas la chaîne de caractères (`string`) `"3"`.

    Grâce aux déclarations de types, **FastAPI** fournit du

## Previous Steps Before Starting

There are many cases where you want to perform some steps **before starting** your application.

For example, you might want to run **database migrations**.

But in most cases, you will want to perform these steps only **once**.

So, you will want to have a **single process** to perform those **previous steps**, before starting the application.

```Python hl_lines="3" title="app/internal/admin.py"
{!../../../docs_src/bigger_applications/app/internal/admin.py!}
```

But we still want to set a custom `prefix` when including the `APIRouter` so that all its *path operations* start with `/admin`, we want to secure it with the `dependencies` we already have for this project, and we want to include `tags` and `responses`.

C'est pourquoi il est logique d'utiliser du code asynchrone ⏸🔀⏯ pour des APIs web.

Ce type d'asynchronicité est ce qui a rendu NodeJS populaire (bien que NodeJS ne soit pas parallèle) et c'est la force du Go en tant que langage de programmation.

Et c'est le même niveau de performance que celui obtenu avec **FastAPI**.

If you want to play with JWT tokens and see how they work, check <a href="https://jwt.io/" class="external-link" target="_blank">https://jwt.io</a>.

## Install `python-jose`