dependencies and the dependencies are solved based on the declared types. So, it's not possible to declare more than one "component" that provides a certain type.

Routes are declared in a single place, using functions declared in other places (instead of using decorators that can be placed right on top of the function that handles the endpoint). This is closer to how Django does it than to how Flask (and Starlette) does it. It separates in the code things that are relatively tightly coupled....

            max_length=max_length,
            discriminator=discriminator,
            multiple_of=multiple_of,
            allow_nan=allow_inf_nan,
            max_digits=max_digits,
            decimal_places=decimal_places,
            **extra,
        )
        if examples is not None:
            kwargs["examples"] = examples
        if regex is not None:
            warnings.warn(

Construisez ensuite la valeur par défaut de votre paramètre avec `Query`, en choisissant 50 comme `max_length` :

```Python hl_lines="9"
{!../../../docs_src/query_params_str_validations/tutorial002.py!}
```

Comme nous devons remplacer la valeur par défaut `None` dans la fonction par `Query()`, nous pouvons maintenant définir la valeur par défaut avec le paramètre `Query(default=None)`, il sert le même objectif qui est de définir cette valeur par défaut.

Donc :

    This way, multiple dependencies can have different scopes, even when used in the
    same *path operation*. And with this, you can access all the scopes required in
    all those dependencies in a single place.

    Read more about it in the
    [FastAPI docs for OAuth2 scopes](https://fastapi.tiangolo.com/advanced/security/oauth2-scopes/).
    """

    def __init__(
        self,
        scopes: Annotated[

```

</div>

### Docs Structure

The documentation uses <a href="https://www.mkdocs.org/" class="external-link" target="_blank">MkDocs</a>.

And there are extra tools/scripts in place to handle translations in `./scripts/docs.py`.

!!! tip
    You don't need to see the code in `./scripts/docs.py`, you just use it in the command line.

### We Make Mistakes

We, as humans, make **mistakes**, all the time. Software almost *always* has **bugs** hidden in different places. 🐛

And we as developers keep improving the code as we find those bugs and as we implement new features (possibly adding new bugs too 😅).

### Small Errors Automatically Handled

```Python hl_lines="2"
{!../../../docs_src/python_types/tutorial004.py!}
```

## Declaring types

You just saw the main place to declare type hints. As function parameters.

This is also the main place you would use them with **FastAPI**.

### Simple types

You can declare all the standard Python types, not only `str`.

You can use, for example:

* `int`

À la place, en étant "asynchrone", une fois terminée, une tâche peut légèrement attendre (quelques microsecondes) que l'ordinateur / le programme finisse ce qu'il était en train de faire, et revienne récupérer le résultat.

We are going to include this `APIRouter` in the main `FastAPI` app, but first, let's check the dependencies and another `APIRouter`.

## Dependencies

We see that we are going to need some dependencies used in several places of the application.

So we put them in their own `dependencies` module (`app/dependencies.py`).

We will now use a simple dependency to read a custom `X-Token` header:

=== "Python 3.9+"

The **default** value of the **function parameter** is the **actual default** value, that's more intuitive with Python in general. 😌