It's relatively tightly coupled with relational databases (like MySQL or PostgreSQL), so, having a NoSQL database (like Couchbase, MongoDB, Cassandra, etc) as the main store engine is not very easy.

{!../../../docs_src/path_params/tutorial002.py!}
```

In this case, `item_id` is declared to be an `int`.

!!! 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>

```

</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.

```

Ici, `item_id` est déclaré comme `int`.

!!! check "vérifier"
    Ceci vous permettra d'obtenir des fonctionnalités de l'éditeur dans votre fonction, telles
    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

<img src="/img/tutorial/generate-clients/image08.png">

## Benefits

When using the automatically generated clients you would get **autocompletion** for:

* Methods.
* Request payloads in the body, query parameters, etc.
* Response payloads.

You would also have **inline errors** for everything.

For example "**Python 3.6+**" means it's compatible with Python 3.6 or above (including 3.7, 3.8, 3.9, 3.10, etc). And "**Python 3.9+**" means it's compatible with Python 3.9 or above (including 3.10, etc).

If you can use the **latest versions of Python**, use the examples for the latest version, those will have the **best and simplest syntax**, for example, "**Python 3.10+**".

## Separating tests

In a real application, you probably would have your tests in a different file.

And your **FastAPI** application might also be composed of several files/modules, etc.

### **FastAPI** app file

Let's say you have a file structure as described in [Bigger Applications](bigger-applications.md){.internal-link target=_blank}:

```
.
├── app
│   ├── __init__.py
│   └── main.py

!!! note
    Vous pouvez uniquement utiliser `await` dans les fonctions créées avec `async def`.

---

Si vous utilisez une bibliothèque externe qui communique avec quelque chose (une BDD, une API, un système de fichiers, etc.) et qui ne supporte pas l'utilisation d'`await` (ce qui est actuellement le cas pour la majorité des bibliothèques de BDD), alors déclarez vos *fonctions de chemin* normalement, avec le classique `def`, comme ceci :

This code is something you can actually use in your application, save the password hashes in your database, etc.

We are going to start from where we left in the previous chapter and increment it.

## About JWT

JWT means "JSON Web Tokens".

```

!!! note
    Você só pode usar `await` dentro de funções criadas com `async def`.

---

Se você está usando biblioteca de terceiros que se comunica com alguma coisa (um banco de dados, uma API, sistema de arquivos etc) e não tem suporte para utilizar `await` (esse é atualmente o caso para a maioria das bibliotecas de banco de dados), então declare suas *funções de operação de rota* normalmente, com apenas `def`, como:

```Python hl_lines="2"