# Get main dependencies
    dependencies: List[str] = metadata.get("dependencies", [])
    # Add optional dependencies to the default dependencies for this (non-slim) package
    for include_optional in include_optional_dependencies:
        optional_dependencies_group = optional_dependencies.get(include_optional, [])

def create_response_field(
    name: str,
    type_: Type[Any],
    class_validators: Optional[Dict[str, Validator]] = None,
    default: Optional[Any] = Undefined,
    required: Union[bool, UndefinedType] = Undefined,
    model_config: Type[BaseConfig] = BaseConfig,
    field_info: Optional[FieldInfo] = None,
    alias: Optional[str] = None,
    mode: Literal["validation", "serialization"] = "validation",
) -> ModelField:
    """

    ]

[tool.tiangolo._internal-slim-build.packages.fastapi-slim.project]
name = "fastapi-slim"

[tool.tiangolo._internal-slim-build.packages.fastapi]
include-optional-dependencies = ["standard"]

[tool.tiangolo._internal-slim-build.packages.fastapi.project.optional-dependencies]
all = [
    # # For the test client
    "httpx >=0.23.0",
    # For templates
    "jinja2 >=2.11.2",
    # For forms and file uploads

```Python hl_lines="9"
{!../../../docs_src/query_params_str_validations/tutorial006c.py!}
```

!!! tip
    Pydantic 是 FastAPI 中所有数据验证和序列化的核心，当你在没有设默认值的情况下使用 `Optional` 或 `Union[Something, None]` 时，它具有特殊行为，你可以在 Pydantic 文档中阅读有关<a href="https://docs.pydantic.dev/latest/concepts/models/#required-optional-fields" class="external-link" target="_blank">必需可选字段</a>的更多信息。

### 使用Pydantic中的`Required`代替省略号(`...`)

如果你觉得使用 `...` 不舒服，你也可以从 Pydantic 导入并使用 `Required`：

        ],
        scheme_name: Annotated[
            Optional[str],
            Doc(
                """
                Security scheme name.

                It will be included in the generated OpenAPI (e.g. visible at `/docs`).
                """
            ),
        ] = None,
        description: Annotated[
            Optional[str],
            Doc(
                """

    And your *path operation* has a little lock in the top-right corner that you can click.

And if you click it, you have a little authorization form to type a `username` and `password` (and other optional fields):

<img src="/img/tutorial/security/image02.png">

!!! note
    It doesn't matter what you type in the form, it won't work yet. But we'll get there.

from typing import Optional

import pytest
from dirty_equals import HasRepr, IsDict, IsOneOf
from fastapi import Depends, FastAPI
from fastapi.exceptions import ResponseValidationError
from fastapi.testclient import TestClient

from .utils import needs_pydanticv2


@pytest.fixture(name="client")
def get_client():
    from pydantic import BaseModel, ValidationInfo, field_validator

    app = FastAPI()

    class ModelB(BaseModel):

* パラメータが **Pydantic モデル**型で宣言された場合、リクエスト**ボディ**として解釈されます。

!!! note "備考"
    FastAPIは、`= None`があるおかげで、`q`がオプショナルだとわかります。

    `Optional[str]` の`Optional` はFastAPIでは使用されていません（FastAPIは`str`の部分のみ使用します）。しかし、`Optional[str]` はエディタがコードのエラーを見つけるのを助けてくれます。

## Pydanticを使わない方法

    return f"foo bar {query}"


@app.get("/query/optional")
def get_query_optional(query=None):
    if query is None:
        return "foo bar"
    return f"foo bar {query}"


@app.get("/query/int")
def get_query_type(query: int):
    return f"foo bar {query}"


@app.get("/query/int/optional")
def get_query_type_optional(query: Optional[int] = None):
    if query is None:
        return "foo bar"

!!! note
    **FastAPI** saura que la valeur de `q` n'est pas requise grâce à la valeur par défaut `=None`.

    Le type `Optional` dans `Optional[str]` n'est pas utilisé par **FastAPI**, mais sera utile à votre éditeur pour améliorer le support offert par ce dernier et détecter plus facilement des erreurs de type.

## Sans Pydantic