```Python
    from main import app
    ```

!!! warning
    Uvicorn and others support a `--reload` option that is useful during development.

    The `--reload` option consumes much more resources, is more unstable, etc.

    It helps a lot during **development**, but you **shouldn't** use it in **production**.

## Hypercorn with Trio

                            "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`.

        ├── __init__.py
        └── test_sql_app.py
```

## Create the new database session

First, we create a new database session with the new database.

We'll use an in-memory database that persists during the tests instead of the local file `sql_app.db`.

But the rest of the session code is more or less the same, we just copy it.

```Python hl_lines="8-13"
{!../../../docs_src/sql_databases/sql_app/tests/test_sql_app.py!}

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

## 🗃 🛠️

👆 💪 ⚒ 📄 🏑 👈 ⚙️ 🗄 🔧 & 🏧 🛠️ 🩺 ⚜:

| 🔢 | 🆎 | 📛 |
|------------|------|-------------|
| `title` | `str` | 📛 🛠️. |
| `description` | `str` | 📏 📛 🛠️. ⚫️ 💪 ⚙️ ✍. |
| `version` | `string` | ⏬ 🛠️. 👉 ⏬ 👆 👍 🈸, 🚫 🗄. 🖼 `2.5.0`. |
| `terms_of_service` | `str` | 📛 ⚖ 🐕‍🦺 🛠️. 🚥 🚚, 👉 ✔️ 📛. |

!!! info
    Note that the `TestClient` receives data that can be converted to JSON, not Pydantic models.

    If you have a Pydantic model in your test and you want to send its data to the application during testing, you can use the `jsonable_encoder` described in [JSON Compatible Encoder](encoder.md){.internal-link target=_blank}.

## Run it

After that, you just need to install `pytest`:

<div class="termy">

```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` 🏗

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.

Without a data validation system, you would have to do all the checks by hand, in code.