=== "Python 3.10+"

    ```Python hl_lines="1  4-6  9-10  21-22  25-26"
    {!> ../../../docs_src/sql_databases/sql_app_py310/schemas.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="3  6-8  11-12  23-24  27-28"
    {!> ../../../docs_src/sql_databases/sql_app_py39/schemas.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="3  6-8  11-12  23-24  27-28"

`q`はオプショナルですが、もし値が渡されてきた場合には、**50文字を超えないこと**を強制してみましょう。

### `Query`のインポート

そのために、まずは`fastapi`から`Query`をインポートします:

```Python hl_lines="3"
{!../../../docs_src/query_params_str_validations/tutorial002.py!}
```

## デフォルト値として`Query`を使用

パラメータのデフォルト値として使用し、パラメータ`max_length`を50に設定します:

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

=== "🐍 3️⃣.6️⃣ & 🔛"

    ```Python hl_lines="18  23"
    {!> ../../../docs_src/response_model/tutorial001_01.py!}
    ```

=== "🐍 3️⃣.9️⃣ & 🔛"

    ```Python hl_lines="18  23"
    {!> ../../../docs_src/response_model/tutorial001_01_py39.py!}
    ```

=== "🐍 3️⃣.1️⃣0️⃣ & 🔛"

    ```Python hl_lines="16  21"
    {!> ../../../docs_src/response_model/tutorial001_01_py310.py!}

```Python hl_lines="2-4"
{!../../../docs_src/dependencies/tutorial007.py!}
```

The yielded value is what is injected into *path operations* and other dependencies:

```Python hl_lines="4"
{!../../../docs_src/dependencies/tutorial007.py!}
```

The code following the `yield` statement is executed after the response has been delivered:

```Python hl_lines="5-6"

=== "Python 3.10+"

    ```Python hl_lines="8-9"
    {!> ../../../docs_src/dependencies/tutorial001_an_py310.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="8-11"
    {!> ../../../docs_src/dependencies/tutorial001_an_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="9-12"
    {!> ../../../docs_src/dependencies/tutorial001_an.py!}
    ```

=== "Python 3.10+"

    ```Python hl_lines="7  48  55-56  59-60  69-75"
    {!> ../../../docs_src/security/tutorial004_an_py310.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="7  48  55-56  59-60  69-75"
    {!> ../../../docs_src/security/tutorial004_an_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="7  49  56-57  60-61  70-76"

=== "Python 3.10+"

    ```Python hl_lines="22-27"
    {!> ../../../docs_src/schema_extra_example/tutorial003_an_py310.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="22-27"
    {!> ../../../docs_src/schema_extra_example/tutorial003_an_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="23-28"
    {!> ../../../docs_src/schema_extra_example/tutorial003_an.py!}
    ```

=== "Python 3.10+"

    ```Python hl_lines="8-9"
    {!> ../../../docs_src/dependencies/tutorial001_an_py310.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="8-11"
    {!> ../../../docs_src/dependencies/tutorial001_an_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="9-12"
    {!> ../../../docs_src/dependencies/tutorial001_an.py!}
    ```

```Python hl_lines="17"
{!../../../docs_src/path_params/tutorial005.py!}
```

#### Récupérer la *valeur de l'énumération*

Vous pouvez obtenir la valeur réel d'un membre (une chaîne de caractères ici), avec `model_name.value`, ou en général, `votre_membre_d'enum.value` :

```Python hl_lines="20"
{!../../../docs_src/path_params/tutorial005.py!}
```

```Python hl_lines="7"
{!../../../docs_src/first_steps/tutorial001.py!}
```

Это обычная Python функция.

**FastAPI** будет вызывать её каждый раз при получении `GET` запроса к URL "`/`".

В данном случае это асинхронная функция.

---

Вы также можете определить ее как обычную функцию вместо `async def`:

```Python hl_lines="7"
{!../../../docs_src/first_steps/tutorial003.py!}