```Python
q: Union[str, None] = Query(default=None, max_length=50)
```

これにより、データを検証し、データが有効でない場合は明確なエラーを表示し、OpenAPIスキーマの　*path operation* にパラメータを記載します。

## バリデーションをさらに追加する

パラメータ`min_length`も追加することができます:

{* ../../docs_src/query_params_str_validations/tutorial003.py hl[10] *}

## 正規表現の追加

パラメータが一致するべき<abbr title="正規表現とは、文字列の検索パターンを定義する文字列です。">正規表現</abbr>を定義することができます:

## Больше валидаций { #add-more-validations }

Можно также добавить параметр `min_length`:

{* ../../docs_src/query_params_str_validations/tutorial003_an_py310.py hl[10] *}

## Регулярные выражения { #add-regular-expressions }

            {
                "type": "string_too_short",
                "loc": ["query", "q"],
                "msg": "String should have at least 3 characters",
                "input": "qu",
                "ctx": {"min_length": 3},
            }
        ]
    }


def test_query_params_str_validations_q_too_long(client: TestClient):
    response = client.get("/items/", params={"q": "q" * 51})
    assert response.status_code == 422

            {
                "type": "string_too_short",
                "loc": ["query", "q"],
                "msg": "String should have at least 3 characters",
                "input": "fa",
                "ctx": {"min_length": 3},
            }
        ]
    }


def test_openapi_schema(client: TestClient):
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text

## Mehr Validierungen hinzufügen { #add-more-validations }

Sie können auch einen `min_length`-Parameter hinzufügen:

{* ../../docs_src/query_params_str_validations/tutorial003_an_py310.py hl[10] *}

## Reguläre Ausdrücke hinzufügen { #add-regular-expressions }

## Adicione mais validações { #add-more-validations }

Você também pode adicionar um parâmetro `min_length`:

{* ../../docs_src/query_params_str_validations/tutorial003_an_py310.py hl[10] *}

## Adicione expressões regulares { #add-regular-expressions }

            {
                "type": "string_too_short",
                "loc": ["query", "q"],
                "msg": "String should have at least 3 characters",
                "input": "fa",
                "ctx": {"min_length": 3},
            }
        ]
    }


def test_openapi_schema(client: TestClient):
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text

## Agregar más validaciones { #add-more-validations }

También puedes agregar un parámetro `min_length`:

{* ../../docs_src/query_params_str_validations/tutorial003_an_py310.py hl[10] *}

## Agregar expresiones regulares { #add-regular-expressions }

    }

    @Override
    public int hashCode() {
        return items.hashCode();
    }

    // CHECKSTYLE_OFF: LineLength

    /**
     * Main to test version parsing and comparison.
     * <p>
     * To check how "1.2.7" compares to "1.2-SNAPSHOT", for example, you can issue

                "type": "string_too_short",
                "loc": ["path", "item_id"],
                "msg": "String should have at least 3 characters",
                "input": "fo",
                "ctx": {"min_length": 3},
            }
        ]
    }


def test_path_param_maxlength_foo():
    response = client.get("/path/param-maxlength/foo")
    assert response.status_code == 200