* **FastAPI**:
    * The same way that Starlette uses Uvicorn and cannot be faster than it, **FastAPI** uses Starlette, so it cannot be faster than it.
    * FastAPI provides more features on top of Starlette. Features that you almost always need when building APIs, like data validation and serialization. And by using it, you get automatic documentation for free (the automatic documentation doesn't even add overhead to running applications, it is generated on startup).

    Again, you can combine `dataclasses` with standard type annotations.

8. Notice that this *path operation function* uses regular `def` instead of `async def`.

    As always, in FastAPI you can combine `def` and `async def` as needed.

## Running on Startup

In most cases, when you create a web API, you want it to be **always running**, uninterrupted, so that your clients can always access it. This is of course, unless you have a specific reason why you want it to run only in certain situations, but most of the time you want it constantly running and **available**.

Similarly, you cannot redefine a path operation:

```Python hl_lines="6  11"
{!../../../docs_src/path_params/tutorial003b.py!}
```

The first one will always be used since the path matches first.

## Predefined values

```Python hl_lines="1  4"
{!../../../docs_src/python_types/tutorial009.py!}
```

Using `Optional[str]` instead of just `str` will let the editor help you detecting errors where you could be assuming that a value is always a `str`, when it could actually be `None` too.

`Optional[Something]` is actually a shortcut for `Union[Something, None]`, they are equivalent.

This also means that in Python 3.10, you can use `Something | None`:

* The **output model** should not have a password.
* The **database model** would probably need to have a hashed password.

!!! danger
    Never store user's plaintext passwords. Always store a "secure hash" that you can then verify.

    If you don't know, you will learn what a "password hash" is in the [security chapters](security/simple-oauth2.md#password-hashing){.internal-link target=_blank}.

Le tout de manière à offrir la meilleure expérience de développement à tous les développeurs.

## Exigences

Après avoir testé plusieurs alternatives, j'ai décidé que j'allais utiliser <a href="https://docs.pydantic.dev/" class="external-link" target="_blank">**Pydantic**</a> pour ses avantages.

💖:

```
http://127.0.0.1:8000/items/?item-query=foobaritems
```

✋️ `item-query` 🚫 ☑ 🐍 🔢 📛.

🔐 🔜 `item_query`.

✋️ 👆 💪 ⚫️ ⚫️❔ `item-query`...

⤴️ 👆 💪 📣 `alias`, & 👈 📛 ⚫️❔ 🔜 ⚙️ 🔎 🔢 💲:

=== "🐍 3️⃣.6️⃣ & 🔛"

    ```Python hl_lines="9"
    {!> ../../../docs_src/query_params_str_validations/tutorial009.py!}
    ```

=== "🐍 3️⃣.1️⃣0️⃣ & 🔛"

!!! tip
    但是依然建议你使用上面提到的主意，使用多个类而不是这些参数。

    这是因为即使使用 `response_model_include` 或 `response_model_exclude` 来省略某些属性，在应用程序的 OpenAPI 定义（和文档）中生成的 JSON Schema 仍将是完整的模型。

    这也适用于作用类似的 `response_model_by_alias`。

```Python hl_lines="31  37"
{!../../../docs_src/response_model/tutorial005.py!}
```

!!! tip
    `{"name", "description"}` 语法创建一个具有这两个值的 `set`。

    等同于 `set(["name", "description"])`。

    それでも、これらのパラメータではなく、複数のクラスを使用して、上記のようなアイデアを使うことをおすすめします。

    これは`response_model_include`や`response_mode_exclude`を使用していくつかの属性を省略しても、アプリケーションのOpenAPI（とドキュメント）で生成されたJSON Schemaが完全なモデルになるからです。

    同様に動作する`response_model_by_alias`にも当てはまります。

```Python hl_lines="31 37"
{!../../../docs_src/response_model/tutorial005.py!}
```

!!! tip "豆知識"
    `{"name", "description"}`の構文はこれら２つの値をもつ`set`を作成します。