"type": "string"
                        }
                    },
                    "msg": {
                        "title": "Message",
                        "type": "string"
                    },
                    "type": {
                        "title": "Error Type",
                        "type": "string"
                    }
                }
            },

```JSON
{"item_id":3}
```

!!! check
    Notice that the value your function received (and returned) is `3`, as a Python `int`, not a string `"3"`.

    So, with that type declaration, **FastAPI** gives you automatic request <abbr title="converting the string that comes from an HTTP request into Python data">"parsing"</abbr>.

## Data validation

# Paramètres de chemin

Vous pouvez déclarer des "paramètres" ou "variables" de chemin avec la même syntaxe que celle utilisée par le
<a href="https://docs.python.org/fr/3/library/string.html#format-string-syntax" class="external-link" target="_blank">formatage de chaîne Python</a> :


```Python hl_lines="6-7"
{!../../../docs_src/path_params/tutorial001.py!}
```

La valeur du paramètre `item_id` sera transmise à la fonction dans l'argument `item_id`.

Digamos que quieres devolver una respuesta <a href="https://en.wikipedia.org/wiki/XML" class="external-link" target="_blank">XML</a>.

Podrías poner tu contenido XML en un string, ponerlo en una `Response` y devolverlo:

```Python hl_lines="1  18"
{!../../../docs_src/response_directly/tutorial002.py!}
```

## Notas

 ╰──────────────────────────╯

<font color="#3465A4">INFO    </font> Using import string <font color="#8AE234"><b>main:app</b></font>

 <font color="#4E9A06">╭─────────── FastAPI CLI - Production mode ───────────╮</font>
 <font color="#4E9A06">│                                                     │</font>
 <font color="#4E9A06">│  Serving at: http://0.0.0.0:8000                    │</font>

👆 💪 ⚒ 👫 ⏩:

```Python hl_lines="36-42"
{!../../../docs_src/nosql_databases/tutorial001.py!}
```

### Ⓜ-🎻

🚥 👆 🚫 😰 ⏮️ `f"userprofile::{username}"`, ⚫️ 🐍 "<a href="https://docs.python.org/3/glossary.html#term-f-string" class="external-link" target="_blank">Ⓜ-🎻</a>".

🙆 🔢 👈 🚮 🔘 `{}` Ⓜ-🎻 🔜 ↔ / 💉 🎻.

### `dict` 🏗

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-03-swagger-02.png)

* Thay thế với tài liệu API với <a href="https://github.com/Rebilly/ReDoc" class="external-link" target="_blank"><strong>ReDoc</strong></a>.

    ```

## Set-Typen

Aber dann denken wir darüber nach und stellen fest, dass sich die Tags nicht wiederholen sollen, es sollen eindeutige Strings sein.

Python hat einen Datentyp speziell für Mengen eindeutiger Dinge: das <abbr title="Menge">`set`</abbr>.

Deklarieren wir also `tags` als Set von Strings.

=== "Python 3.10+"

    ```Python hl_lines="12"
    {!> ../../../docs_src/body_nested_models/tutorial003_py310.py!}
    ```

Another big feature needed by APIs is data validation, making sure that the data is valid, given certain parameters. For example, that some field is an `int`, and not some random string. This is especially useful for incoming data.