## Usar `Union` u `Optional` { #using-union-or-optional }

Si por alguna razón tu código no puede usar `|`, por ejemplo si no está en una anotación de tipos sino en algo como `response_model=`, en lugar de usar la barra vertical (`|`) puedes usar `Union` de `typing`.

Por ejemplo, podrías declarar que algo podría ser un `str` o `None`:

```python
from typing import Union


def say_hi(name: Union[str, None]):

        when(mockNdrBuffer.dec_ndr_long()).thenReturn(1, 123); // _infop, retval
        when(mockNdrBuffer.dec_ndr_short()).thenReturn((int) (short) 0); // union discriminant

        queryInfoPolicy.decode_out(mockNdrBuffer);

        verify(mockInfo).decode(mockNdrBuffer);
        assertEquals(123, queryInfoPolicy.retval);
    }

    @Test

## `Union` 또는 `anyOf` { #union-or-anyof }

두 가지 이상의 타입을 포함하는 `Union`으로 응답을 선언할 수 있습니다. 이는 응답이 그 중 하나의 타입일 수 있음을 의미합니다.

OpenAPI에서는 이를 `anyOf`로 정의합니다.

이를 위해 표준 Python 타입 힌트인 [`typing.Union`](https://docs.python.org/3/library/typing.html#typing.Union)을 사용할 수 있습니다:

/// note

  // Element-level accessors
  //

  /**
   * Returns a live view of the edges whose {@link #incidentNodes(Object) incident nodes} in this
   * network include {@code node}.
   *
   * <p>This is equal to the union of {@link #inEdges(Object)} and {@link #outEdges(Object)}.
   *
   * <p>If {@code node} is removed from the network after this method is called, the {@code Set}

conditions for use, reproduction, and distribution as defined by Sections 1 through 9 of this document. "Licensor" shall mean the copyright owner or entity authorized by the copyright owner that is granting the License. "Legal Entity" shall mean the union of the acting entity and all other entities that control, are controlled by, or are under common control with that entity. For the purposes of this definition, "control" means (i) the power, direct or indirect, to cause the direction or management...

## `Union` または `anyOf` { #union-or-anyof }

レスポンスを2つ以上の型の`Union`として宣言できます。つまり、そのレスポンスはそれらのいずれかになります。

OpenAPIでは`anyOf`で定義されます。

そのためには、標準的なPythonの型ヒント[`typing.Union`](https://docs.python.org/3/library/typing.html#typing.Union)を使用します:

/// note | 備考

	if wantFormat := h.Format; wantFormat != FormatUnknown {
		if wantFormat.has(FormatPAX) && !preferPAX {
			wantFormat.mayBe(FormatUSTAR) // PAX implies USTAR allowed too
		}
		format.mayOnlyBe(wantFormat) // Set union of formats allowed and format wanted
	}
	if format == FormatUnknown {
		switch h.Format {
		case FormatUSTAR:
			err = headerError{"Format specifies USTAR", whyNoUSTAR, whyOnlyPAX, whyOnlyGNU}
		case FormatPAX:

	jt := JoinTable{UserID: 1, FriendID: 2}
	err := DB.Create(&jt).Error
	if err != nil {
		t.Errorf("No error should happen when create a record without a GORM primary key. But in the database this primary key exists and is the union of 2 or more fields\n But got: %s", err)
	}
}

func TestSelectWithCreate(t *testing.T) {

#### Union { #union }

Puedes declarar que una variable puede ser cualquiera de **varios tipos**, por ejemplo, un `int` o un `str`.

Para definirlo usas la <dfn title='también llamado "operador OR a nivel de bits", pero ese significado no es relevante aquí'>barra vertical (`|`)</dfn> para separar ambos tipos.

## 回應模型編碼參數 { #response-model-encoding-parameters }

你的回應模型可能有預設值，例如：

{* ../../docs_src/response_model/tutorial004_py310.py hl[9,11:12] *}

* `description: Union[str, None] = None`（或在 Python 3.10 中的 `str | None = None`）預設為 `None`。
* `tax: float = 10.5` 預設為 `10.5`。
* `tags: List[str] = []` 預設為空的 list：`[]`。

但如果這些值其實沒有被儲存，你可能想要在結果中省略它們。