Ouvrez votre navigateur à l'adresse <a href="http://127.0.0.1:8000" class="external-link" target="_blank">http://127.0.0.1:8000</a>.

Vous obtiendrez cette réponse JSON :

```JSON
{"message": "Hello World"}
```

### Documentation interactive de l'API

Rendez-vous sur <a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a>.

* <a href="https://speakeasy.com/editor?utm_source=fastapi+repo&utm_medium=github+sponsorship" class="external-link" target="_blank">Speakeasy</a>
* <a href="https://www.stainless.com/?utm_source=fastapi&utm_medium=referral" class="external-link" target="_blank">Stainless</a>
* <a href="https://developers.liblab.com/tutorials/sdk-for-fastapi?utm_source=fastapi" class="external-link" target="_blank">liblab</a>

Because of this, **FastAPI** itself provides an alternative API documentation (using ReDoc), which you can access at <a href="http://127.0.0.1:8000/redoc" class="external-link" target="_blank">http://127.0.0.1:8000/redoc</a>:

<img src="/img/tutorial/path-params/image02.png">

Graças ao <a href="https://www.starlette.dev/testclient/" class="external-link" target="_blank">Starlette</a>, testar aplicações **FastAPI** é fácil e agradável.

Ele é baseado no <a href="https://www.python-httpx.org" class="external-link" target="_blank">HTTPX</a>, que por sua vez é projetado com base em Requests, por isso é muito familiar e intuitivo.

* <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Forwarded-Proto" class="external-link" target="_blank">X-Forwarded-Proto</a>
* <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Forwarded-Host" class="external-link" target="_blank">X-Forwarded-Host</a>

///

<small>* estimation based on tests conducted by an internal development team, building production applications.</small>

## Sponsors

<!-- sponsors -->

* <a href="https://hub.docker.com/_/postgres" class="external-link" target="_blank">PostgreSQL</a>
* <a href="https://hub.docker.com/_/mysql" class="external-link" target="_blank">MySQL</a>
* <a href="https://hub.docker.com/_/mongo" class="external-link" target="_blank">MongoDB</a>
* <a href="https://hub.docker.com/_/redis" class="external-link" target="_blank">Redis</a>, etc.

Некоторые другие облачные провайдеры ✨ [**спонсируют FastAPI**](../help-fastapi.md#sponsor-the-author){.internal-link target=_blank} ✨ тоже. 🙇

Возможно, вы захотите попробовать их сервисы и воспользоваться их руководствами:

* <a href="https://docs.render.com/deploy-fastapi?utm_source=deploydoc&utm_medium=referral&utm_campaign=fastapi" class="external-link" target="_blank">Render</a>

### Use cases: external service { #use-cases-external-service }

An example could be that you have an external authentication provider that you need to call.

You send it a token and it returns an authenticated user.

    This will (let's imagine) let the API user (some external developer) create an
    invoice.

    And this path operation will:

    * Send the invoice to the client.
    * Collect the money from the client.
    * Send a notification back to the API user (the external developer), as a callback.
        * At this point is that the API will somehow send a POST request to the
            external API with the notification of the invoice event