Imagine que você queira que um parâmetro tenha o nome `item-query`.

Desta maneira:

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

Mas o nome `item-query` não é um nome de váriavel válido no Python.

O que mais se aproxima é `item_query`.

Mas ainda você precisa que o nome seja exatamente `item-query`...

    ```

👥 ✔️ ❎ 🔢 💲 `None` 🔢 ⏮️ `Query()`, 👥 💪 🔜 ⚒ 🔢 💲 ⏮️ 🔢 `Query(default=None)`, ⚫️ 🍦 🎏 🎯 ⚖ 👈 🔢 💲.

:

```Python
q: Union[str, None] = Query(default=None)
```

...⚒ 🔢 📦, 🎏:

```Python
q: Union[str, None] = None
```

& 🐍 3️⃣.1️⃣0️⃣ & 🔛:

```Python
q: str | None = Query(default=None)
```

...⚒ 🔢 📦, 🎏:

```Python
q: str | None = None
```

### `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!}
```

我们打算添加约束条件：即使 `q` 是可选的，但只要提供了该参数，则该参数值**不能超过50个字符的长度**。

### 导入 `Query`

为此，首先从 `fastapi` 导入 `Query`：

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

## 使用 `Query` 作为默认值

现在，将 `Query` 用作查询参数的默认值，并将它的 `max_length` 参数设置为 50：

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

由于我们必须用 `Query(default=None)` 替换默认值 `None`，`Query` 的第一个参数同样也是用于定义默认值。

http://127.0.0.1:8000/items/foo-item
```

... sem adicionar o parâmetro obrigatório `needy`, você verá um erro como:

```JSON
{
    "detail": [
        {
            "loc": [
                "query",
                "needy"
            ],
            "msg": "field required",
            "type": "value_error.missing"
        }
    ]
}
```

在浏览器中打开如下 URL：

```
http://127.0.0.1:8000/items/foo-item
```

……因为路径中没有必选参数 `needy`，返回的响应中会显示如下错误信息：

```JSON
{
    "detail": [
        {
            "loc": [
                "query",
                "needy"
            ],
            "msg": "field required",
            "type": "value_error.missing"
        }
    ]
}
```

`needy` 是必选参数，因此要在 URL 中设置值：

```

🚥 👆 📂 👆 🖥 📛 💖:

```
http://127.0.0.1:8000/items/foo-item
```

...🍵 ❎ ✔ 🔢 `needy`, 👆 🔜 👀 ❌ 💖:

```JSON
{
    "detail": [
        {
            "loc": [
                "query",
                "needy"
            ],
            "msg": "field required",
            "type": "value_error.missing"
        }
    ]
}
```

`needy` 🚚 🔢, 👆 🔜 💪 ⚒ ⚫️ 📛:

```

```

...`needy` parametresini eklemeden açarsanız şuna benzer bir hata ile karşılaşırsınız:

```JSON
{
  "detail": [
    {
      "type": "missing",
      "loc": [
        "query",
        "needy"
      ],
      "msg": "Field required",
      "input": null,
      "url": "https://errors.pydantic.dev/2.1/v/missing"
    }
  ]
}
```

以下のURLをブラウザで開くと:

```
http://127.0.0.1:8000/items/foo-item
```

...必須のパラメータ `needy` を加えなかったので、以下の様なエラーが表示されます:

```JSON
{
    "detail": [
        {
            "loc": [
                "query",
                "needy"
            ],
            "msg": "field required",
            "type": "value_error.missing"
        }
    ]
}
```

`needy` は必須のパラメータなので、URLにセットする必要があります:

```

import org.opensearch.index.query.RangeQueryBuilder;
import org.opensearch.index.query.RegexpQueryBuilder;
import org.opensearch.index.query.SpanTermQueryBuilder;
import org.opensearch.index.query.TermQueryBuilder;
import org.opensearch.index.query.TermsQueryBuilder;
import org.opensearch.index.query.WildcardQueryBuilder;
import org.opensearch.index.query.functionscore.FunctionScoreQueryBuilder;