from typing import Union

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: Union[str, None] = Query(default=None, max_length=50)):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

from pydantic import BaseModel, Field

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = Field(
        default=None, title="The description of the item", max_length=300
    )
    price: float = Field(gt=0, description="The price must be greater than zero")
    tax: float | None = None


@app.put("/items/{item_id}")

            {
                "type": "string_too_long",
                "loc": ["query", "q"],
                "msg": "String should have at most 50 characters",
                "input": "q" * 51,
                "ctx": {"max_length": 50},
            }
        ]
    }


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

`Optional` の部分は、エディターによるより良いサポートを可能にします。

///

そして、さらに多くのパラメータを`Query`に渡すことができます。この場合、文字列に適用される、`max_length`パラメータを指定します。

```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

from pydantic import BaseModel, Field

app = FastAPI()


class Item(BaseModel):
    name: str
    description: Union[str, None] = Field(
        default=None, title="The description of the item", max_length=300
    )
    price: float = Field(gt=0, description="The price must be greater than zero")
    tax: Union[float, None] = None


@app.put("/items/{item_id}")

from pydantic import BaseModel, Field

app = FastAPI()


class Item(BaseModel):
    name: str
    description: Union[str, None] = Field(
        default=None, title="The description of the item", max_length=300
    )
    price: float = Field(gt=0, description="The price must be greater than zero")
    tax: Union[float, None] = None


@app.put("/items/{item_id}")

                "input": "fo",
                "ctx": {"min_length": 3},
            }
        ]
    }


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


def test_path_param_maxlength_foobar():
    response = client.get("/path/param-maxlength/foobar")
    assert response.status_code == 422

    }

    @Test
    void testWriteSecurityBuffer() {
        // Test writeSecurityBuffer
        byte[] dest = new byte[8]; // Enough for length, max_length, offset
        byte[] src = "Test".getBytes();

        // Test with non-null source array
        int nextOffset = NtlmMessage.writeSecurityBuffer(dest, 0, src);

  /**
   * Maximum length of a full domain name, including separators, and leaving room for the root
   * label. See <a href="http://www.ietf.org/rfc/rfc2181.txt">RFC 2181</a> part 11.
   */
  private static final int MAX_LENGTH = 253;

  /**
   * Maximum size of a single part of a domain name. See <a
   * href="http://www.ietf.org/rfc/rfc2181.txt">RFC 2181</a> part 11.
   */
  private static final int MAX_DOMAIN_PART_LENGTH = 63;

                               void* value, size_t max_length,
                               TF_Status* status) {
  const auto* attr = GetAttrValue(oper, attr_name, status);
  if (!status->status.ok()) return;
  if (attr->value_case() != tensorflow::AttrValue::kS) {
    status->status =
        InvalidArgument("Attribute '", attr_name, "' is not a string");
    return;
  }
  if (max_length <= 0) {
    return;
  }