And there are dozens of alternatives, all based on OpenAPI. You could easily add any of those alternatives to your application built with **FastAPI**.

You could also use it to generate code automatically, for clients that communicate with your API. For example, frontend, mobile or IoT applications.

## Recap, step by step

### Step 1: import `FastAPI`

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

To try it out:

* Open the app with several browser tabs.
* Write messages from them.
* Then close one of the tabs.

That will raise the `WebSocketDisconnect` exception, and all the other clients will receive a message like:

```
Client #1596980209979 left the chat
```

!!! tip
    The app above is a minimal and simple example to demonstrate how to handle and broadcast messages to several WebSocket connections.

* Designed around these standards, after a meticulous study. Instead of an afterthought layer on top.
* This also allows using automatic **client code generation** in many languages.

### Automatic docs

Interactive API documentation and exploration web user interfaces. As the framework is based on OpenAPI, there are multiple options, 2 included by default.

* Converter de e para JSON automaticamente.
* Documentar tudo com OpenAPI, que poderá ser usado por:
    * Sistemas de documentação interativos.
    * Sistemas de clientes de geração de código automáticos, para muitas linguagens.
* Fornecer diretamente 2 interfaces _web_ de documentação interativa.

---

Nós arranhamos apenas a superfície, mas você já tem idéia de como tudo funciona.

    - advanced/testing-database.md
    - advanced/async-tests.md
    - advanced/settings.md
    - advanced/openapi-callbacks.md
    - advanced/openapi-webhooks.md
    - advanced/wsgi.md
    - advanced/generate-clients.md
  - fastapi-cli.md
  - Deployment:
    - deployment/index.md
    - deployment/versions.md
    - deployment/https.md
    - deployment/manually.md
    - deployment/concepts.md
    - deployment/cloud.md

    * İnteraktiv sənədləşmə sistemləri.
    * Bir çox proqramlaşdırma dilləri üçün avtomatlaşdırılmış <abbr title="Müştəri: Client">müştəri</abbr> kodu yaratma sistemləri.
* 2 interaktiv sənədləşmə veb interfeysini birbaşa təmin edəcək.

---

Yeni başlamışıq, amma siz artıq işin məntiqini başa düşmüsünüz.

* Kiểm tra xem có một `item_id` trong đường dẫn với các request `GET` và `PUT` không?
* Kiểm tra xem `item_id` có phải là kiểu `int` trong các request `GET` và `PUT` không?
    * Nếu không, client sẽ thấy một lỗi rõ ràng và hữu ích.
* Kiểm tra xem nếu có một tham số `q` trong query string (ví dụ như `http://127.0.0.1:8000/items/foo?q=somequery`) cho request `GET`.
    * Tham số `q` được định nghĩa `= None`, nó là tùy chọn.

* Valider que `item_id` existe dans le chemin des requêtes `GET` et `PUT`.
* Valider que `item_id` est de type `int` pour les requêtes `GET` et `PUT`.
    * Si ce n'est pas le cas, le client voit une erreur utile et claire.
* Vérifier qu'il existe un paramètre de requête facultatif nommé `q` (comme dans `http://127.0.0.1:8000/items/foo?q=somequery`) pour les requêtes `GET`.

* Validate that there is an `item_id` in the path for `GET` and `PUT` requests.
* Validate that the `item_id` is of type `int` for `GET` and `PUT` requests.
    * If it is not, the client will see a useful, clear error.
* Check if there is an optional query parameter named `q` (as in `http://127.0.0.1:8000/items/foo?q=somequery`) for `GET` requests.
    * As the `q` parameter is declared with `= None`, it is optional.