## About HTTP status codes

!!! note
    If you already know what HTTP status codes are, skip to the next section.

In HTTP, you send a numeric status code of 3 digits as part of the response.

These status codes have a name associated to recognize them, but the important part is the number.

In short:

* `100` and above are for "Information". You rarely use them directly.  Responses with these status codes cannot have a body.

# Query Parameters

When you declare other function parameters that are not part of the path parameters, they are automatically interpreted as "query" parameters.

```Python hl_lines="9"
{!../../../docs_src/query_params/tutorial001.py!}
```

The query is the set of key-value pairs that go after the `?` in a URL, separated by `&` characters.

For example, in the URL:

```
http://127.0.0.1:8000/items/?skip=0&limit=10
```

As part of that, I needed to investigate, test and use many alternatives.

The history of **FastAPI** is in great part the history of its predecessors.

As said in the section [Alternatives](alternatives.md){.internal-link target=_blank}:

<blockquote markdown="1">

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.

This part is pretty normal, most of the code is probably already familiar to you:

```Python hl_lines="9-13  36-53"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

!!! tip

Ich zeige Ihnen einige der wichtigsten Konzepte, die Sie beim Deployment einer **FastAPI**-Anwendung wahrscheinlich berücksichtigen sollten (obwohl das meiste davon auch für jede andere Art von Webanwendung gilt).

!!! info
    Keep in mind that the most important part to make a parameter optional is the part:

    ```Python
    = None
    ```

    or the:

    ```Python
    = Query(default=None)
    ```

    as it will use that `None` as the default value, and that way make the parameter **not required**.

    But when the form includes files, it is encoded as `multipart/form-data`. If you use `File`, **FastAPI** will know it has to get the files from the correct part of the body.

Wenn man sich auf die entfernte Maschine bezieht, wird sie üblicherweise als **Server**, aber auch als **Maschine**, **VM** (virtuelle Maschine) oder **Knoten** bezeichnet. Diese Begriffe beziehen sich auf irgendeine Art von entfernten Rechner, normalerweise unter Linux, auf dem Sie Programme ausführen.

## Das Serverprogramm installieren

Sie können einen ASGI-kompatiblen Server installieren mit:

=== "Uvicorn"

...Mais ici, je veux vous montrer la communauté.

---

**FastAPI** reçoit beaucoup de soutien de la part de la communauté. Et je tiens à souligner leurs contributions.

Ce sont ces personnes qui :

    But because **FastAPI** is based on the Python standards, including `Annotated`, you can use this trick in your code. 😎

The dependencies will keep working as expected, and the **best part** is that the **type information will be preserved**, which means that your editor will be able to keep providing you with **autocompletion**, **inline errors**, etc. The same for other tools like `mypy`.