It had automatic data validation, data serialization and OpenAPI schema generation based on the same type hints in several places.

```

À ne pas confondre avec la déclaration de valeurs par défaut comme ici :

```Python
    first_name="john", last_name="doe"
```

C'est une chose différente.

On utilise un deux-points (`:`), et pas un égal (`=`).

Et ajouter des annotations de types ne crée normalement pas de différence avec le comportement qui aurait eu lieu si elles n'étaient pas là.

La **concurrence** et le **parallélisme** sont tous deux liés à l'idée de "différentes choses arrivant plus ou moins au même moment".

Mais les détails entre la **concurrence** et le **parallélisme** diffèrent sur de nombreux points.

Pour expliquer la différence, voici une histoire de burgers :

#### Burgers concurrents

* If the PR can be simplified in a way, you can ask for that, but there's no need to be too picky, there might be a lot of subjective points of view (and I will have my own as well 🙈), so it's better if you can focus on the fundamental things.

### Tests

* Help me check that the PR has **tests**.

* Check that the tests **fail** before the PR. 🚨

!!! check "vérifier"
    Donc, avec ces mêmes déclarations de type Python, **FastAPI** vous fournit de la validation de données.

    Notez que l'erreur mentionne le point exact où la validation n'a pas réussi.

    Ce qui est incroyablement utile au moment de développer et débugger du code qui interagit avec votre API.

## Documentation

```Python hl_lines="3"
{!../../../docs_src/first_steps/tutorial001.py!}
```

Here the `app` variable will be an "instance" of the class `FastAPI`.

This will be the main point of interaction to create all your API.

### Step 3: create a *path operation*

#### Path

"Path" here refers to the last part of the URL starting from the first `/`.

So, in a URL like:

```

{!../../../docs_src/behind_a_proxy/tutorial004.py!}
```

and then it won't include it in the OpenAPI schema.

## Mounting a sub-application

If you need to mount a sub-application (as described in [Sub Applications - Mounts](sub-applications.md){.internal-link target=_blank}) while also using a proxy with `root_path`, you can do it normally, as you would expect.

We create an `HTTPException` that we can re-use (`raise`) later at several points.

In this exception, we include the scopes required (if any) as a string separated by spaces (using `scope_str`). We put that string containing the scopes in the `WWW-Authenticate` header (this is part of the spec).

### What is a Process

The word **process** is normally used in a more specific way, only referring to the thing that is running in the operating system (like in the last point above):

* A particular program while it is **running** on the operating system.

You would probably get a cloud server (a virtual machine) or something similar, and it would have a <abbr title="That doesn't change">fixed</abbr> **public IP address**.

In the DNS server(s) you would configure a record (an "`A record`") to point **your domain** to the public **IP address of your server**.

You would probably do this just once, the first time, when setting everything up.

!!! tip