Another big feature needed by APIs is data validation, making sure that the data is valid, given certain parameters. For example, that some field is an `int`, and not some random string. This is especially useful for incoming data.

Without a data validation system, you would have to do all the checks by hand, in code.

```

</div>

That would work for most of the cases. 😎

You could use that command for example to start your **FastAPI** app in a container, in a server, etc.

## ASGI Servers

Let's go a little deeper into the details.

{!../../../docs_src/query_params_str_validations/tutorial009.py!}
```

## Déprécier des paramètres

Disons que vous ne vouliez plus utiliser ce paramètre désormais.

Il faut qu'il continue à exister pendant un certain temps car vos clients l'utilisent, mais vous voulez que la documentation mentionne clairement que ce paramètre est <abbr title="obsolète, recommandé de ne pas l'utiliser">déprécié</abbr>.

"_Мы перешли на **FastAPI** для наших **API** [...] Я думаю, вам тоже понравится [...]_"

---

「_如果你正打算学习一个**现代框架**用来构建 REST API，来看下 **FastAPI** [...] 它快速、易用且易于学习 [...]_」

「_我们已经将 **API** 服务切换到了 **FastAPI** [...] 我认为你会喜欢它的 [...]_」

                It is UTF-8-encoded data. The interpretation of the reason is up to the
                application, it is not specified by the WebSocket specification.

                It could contain text that could be human-readable or interpretable
                by the client code, etc.
                """
            ),
        ] = None,
    ) -> None:
        super().__init__(code=code, reason=reason)

* `Form()`
* `File()`

The keys of the `dict` identify each example, and each value is another `dict`.

Each specific example `dict` in the `examples` can contain:

* `summary`: Short description for the example.
* `description`: A long description that can contain Markdown text.
* `value`: This is the actual example shown, e.g. a `dict`.

    The correct place is:

    * In the key `content`, that has as value another JSON object (`dict`) that contains:
        * A key with the media type, e.g. `application/json`, that contains as value another JSON object, that contains:
            * A key `schema`, that has as the value the JSON Schema from the model, here's the correct place.

!!! tip
    Keep in mind that JSON only supports `str` as keys.

    But Pydantic has automatic data conversion.

    This means that, even though your API clients can only send strings as keys, as long as those strings contain pure integers, Pydantic will convert them and validate them.

    And the `dict` you receive as `weights` will actually have `int` keys and `float` values.

## Recap

            "termsOfService": "http://example.com/terms/",
            "contact": {
                "name": "Deadpoolio the Amazing",
                "url": "http://x-force.example.com/contact/",
                "email": "******@****.***",
            },
            "license": {
                "name": "Apache 2.0",