```Python
q: Union[str, None] = Query(default=None, max_length=50)
```

Cela va valider les données, montrer une erreur claire si ces dernières ne sont pas valides, et documenter le paramètre dans le schéma `OpenAPI` de cette *path operation*.

## Rajouter plus de validation

Vous pouvez aussi rajouter un second paramètre `min_length` :

    * des erreurs automatiques et claires lorsque les données ne sont pas valides.
    * une validation même pour les objets <abbr title="JavaScript Object Notation">JSON</abbr> profondément imbriqués.
* <abbr title="aussi connu sous le nom de : serialization, parsing, marshalling">Une conversion</abbr> des données d'entrée : venant du réseau et allant vers les données et types de Python, permettant de lire :

    of computer software code that is originally released under this
    License.

    1.11. "Patent Claims" means any patent claim(s), now owned or
    hereafter acquired, including without limitation, method, process,
    and apparatus claims, in any patent Licensable by grantor.

    1.12. "Source Code" means (a) the common form of computer software

org.sonatype.aether:aether-impl
org.sonatype.aether:aether-spi
org.sonatype.aether:aether-util

------------------------------------------------------------------------------
3-Clause BSD
https://opensource.org/licenses/BSD-3-Clause

com.google.code.findbugs:jsr305

org.hamcrest:hamcrest-core
BSD License

Copyright (c) 2000-2015 www.hamcrest.org
All rights reserved.

that Commercial Contributor then makes performance claims, or offers warranties
related to Product X, those performance claims and warranties are such Commercial
Contributor's responsibility alone. Under this section, the Commercial Contributor
would have to defend claims against the other Contributors related to those
performance claims and warranties, and if a court requires any other Contributor

### Étape 1 : import `FastAPI`

```Python hl_lines="1"
{!../../../docs_src/first_steps/tutorial001.py!}
```

`FastAPI` est une classe Python qui fournit toutes les fonctionnalités nécessaires au lancement de votre API.

!!! note "Détails techniques"
    `FastAPI` est une classe héritant directement de `Starlette`.

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