que des vérifications d'erreur, de l'auto-complétion, etc.

## <abbr title="aussi appelé sérialisation, ou parfois parsing ou marshalling en anglais">Conversion</abbr> de données

Si vous exécutez cet exemple et allez sur <a href="http://127.0.0.1:8000/items/3" class="external-link" target="_blank">http://127.0.0.1:8000/items/3</a>, vous aurez comme réponse :

```JSON
{"item_id":3}

!!! check
    This will give you editor support inside of your function, with error checks, completion, etc.

## Data <abbr title="also known as: serialization, parsing, marshalling">conversion</abbr>

If you run this example and open your browser at <a href="http://127.0.0.1:8000/items/3" class="external-link" target="_blank">http://127.0.0.1:8000/items/3</a>, you will see a response of:

```JSON
{"item_id":3}

### <a href="https://marshmallow.readthedocs.io/en/stable/" class="external-link" target="_blank">Marshmallow</a>

### <a href="https://marshmallow.readthedocs.io/en/stable/" class="external-link" target="_blank">🍭</a>

1️⃣ 👑 ⚒ 💪 🛠️ ⚙️ 📊 "<abbr title="also called marshalling, conversion">🛠️</abbr>" ❔ ✊ 📊 ⚪️➡️ 📟 (🐍) &amp; 🏭 ⚫️ 🔘 🕳 👈 💪 📨 🔘 🕸. 🖼, 🏭 🎚 ⚗ 📊 ⚪️➡️ 💽 🔘 🎻 🎚. 🏭 `datetime` 🎚 🔘 🎻, ♒️.

➕1️⃣ 🦏 ⚒ 💚 🔗 💽 🔬, ⚒ 💭 👈 💽 ☑, 🤝 🎯 🔢. 🖼, 👈 🏑 `int`, &amp; 🚫 🎲 🎻. 👉 ✴️ ⚠ 📨 💽.

            Read more about it in the
            [FastAPI docs for Header Parameters](https://fastapi.tiangolo.com/tutorial/header-params/#automatic-conversion)
            """
        ),
    ] = True,
    title: Annotated[
        Optional[str],
        Doc(
            """
            Human-readable title.
            """
        ),

    }
}
```

!!! note
    Notice that even though the `item` was declared the same way as before, it is now expected to be inside of the body with a key `item`.


**FastAPI** will do the automatic conversion from the request, so that the parameter `item` receives it's specific content and the same for `user`.

It will perform the validation of the compound data, and will document it like that for the OpenAPI schema and automatic docs.

### <a href="https://marshmallow.readthedocs.io/en/3.0/" class="external-link" target="_blank">Marshmallow</a>

APIシステムで必要とされる主な機能の一つに、コード (Python) からデータを取り出して、ネットワークを介して送れるものに変換するデータの「<abbr title="marshalling, conversion">シリアライゼーション</abbr>」があります。例えば、データベースのデータを含むオブジェクトをJSONオブジェクトに変換したり、`datetime` オブジェクトを文字列に変換するなどです。

Toutes les fonctionnalités qui s'appliquent aux paramètres de chemin s'appliquent aussi aux paramètres de requête :

* Support de l'éditeur : vérification d'erreurs, auto-complétion, etc.
* <abbr title="conversion de la chaîne de caractères venant de la requête HTTP en données Python">"Parsing"</abbr> de données.
* Validation de données.
* Annotations d'API et documentation automatique.

## Valeurs par défaut

        "name": "The Foo live"
    }
}
```

Again, doing just that declaration, with **FastAPI** you get:

* Editor support (completion, etc.), even for nested models
* Data conversion
* Data validation
* Automatic documentation

## Special types and validation

Apart from normal singular types like `str`, `int`, `float`, etc. you can use more complex singular types that inherit from `str`.

!!! check
    Also notice that **FastAPI** is smart enough to notice that the path parameter `item_id` is a path parameter and `q` is not, so, it's a query parameter.

## Query parameter type conversion

You can also declare `bool` types, and they will be converted:

=== "Python 3.10+"

    ```Python hl_lines="7"
    {!> ../../../docs_src/query_params/tutorial003_py310.py!}
    ```

=== "Python 3.8+"