## 预设值

路径操作使用 Python 的 <abbr title="Enumeration">`Enum`</abbr> 类型接收预设的*路径参数*。

### 创建 `Enum` 类

导入 `Enum` 并创建继承自 `str` 和 `Enum` 的子类。

通过从 `str` 继承，API 文档就能把值的类型定义为**字符串**，并且能正确渲染。

然后，创建包含固定值的类属性，这些固定值是可用的有效值：

{* ../../docs_src/path_params/tutorial005.py hl[1,6:9] *}

/// info | 说明

Python 3.4 及之后版本支持<a href="https://docs.python.org/zh-cn/3/library/enum.html" class="external-link" target="_blank">枚举（即 enums）</a>。

 * @author Jared Levy
 */
@J2ktIncompatible // EnumBimap
@GwtCompatible
@NullMarked
public class EnumBiMapTest extends TestCase {
  private enum Currency {
    DOLLAR,
    FRANC,
    PESO,
    POUND,
    YEN
  }

  private enum Country {
    CANADA,
    CHILE,
    JAPAN,
    SWITZERLAND,
    UK
  }

  @AndroidIncompatible // test-suite builders

### Создание класса `Enum` { #create-an-enum-class }

Импортируйте `Enum` и создайте подкласс, который наследуется от `str` и `Enum`.

Мы наследуемся от `str`, чтобы документация API могла понять, что значения должны быть типа `string` и отображалась правильно.

import java.util.ListIterator;
import java.util.Set;

/**
 * A method supported by implementations of the {@link Iterator} or {@link ListIterator} interface.
 *
 * <p>This enum is GWT compatible.
 *
 * @author Chris Povirk
 */
@GwtCompatible
public enum IteratorFeature {
  /** Support for {@link Iterator#remove()}. */
  SUPPORTS_REMOVE,
  /**
   * Support for {@link ListIterator#add(Object)}; ignored for plain {@link Iterator}

def test_get_enums_invalid():
    response = client.get("/models/foo")
    assert response.status_code == 422
    assert response.json() == {
        "detail": [
            {
                "type": "enum",
                "loc": ["path", "model_name"],
                "msg": "Input should be 'alexnet', 'resnet' or 'lenet'",
                "input": "foo",
                "ctx": {"expected": "'alexnet', 'resnet' or 'lenet'"},

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package gradlebuild.basics

import org.gradle.api.attributes.Attribute


enum class GradleModuleApiAttribute {
    API,
    IMPLEMENTATION;

    companion object {
        val attribute = Attribute.of(GradleModuleApiAttribute::class.java)
    }

        EnumSetAccumulator::toImmutableSet,
        Collector.Characteristics.UNORDERED);
  }

  private static final class EnumSetAccumulator<E extends Enum<E>> {
    @SuppressWarnings({"rawtypes", "unchecked"})
    static final Collector<Enum<?>, ?, ImmutableSet<? extends Enum<?>>> TO_IMMUTABLE_ENUM_SET =
        (Collector) toImmutableEnumSetGeneric();

    private @Nullable EnumSet<E> set;

    void add(E e) {

### Eine `Enum`-Klasse erstellen { #create-an-enum-class }

Importieren Sie `Enum` und erstellen Sie eine Unterklasse, die von `str` und `Enum` erbt.

import warnings
from collections import deque
from dataclasses import dataclass
from datetime import datetime, timezone
from decimal import Decimal
from enum import Enum
from math import isinf, isnan
from pathlib import PurePath, PurePosixPath, PureWindowsPath
from typing import Optional, TypedDict

import pytest
from fastapi._compat import Undefined
from fastapi.encoders import jsonable_encoder

package com.google.common.collect.testing;

import com.google.common.annotations.GwtCompatible;

/**
 * A sample enumerated type we use for testing.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible
public enum AnEnum {
  A,
  B,
  C,
  D,
  E,
  F