兩者等價且底層相同，但我會推薦用 `Union` 而不要用 `Optional`，因為「optional」這個詞看起來會讓人以為這個值是可選的，但實際上它的意思是「可以是 `None`」，即使它不是可選的、仍然是必填。

我認為 `Union[SomeType, None]` 更能清楚表達其含義。

這只是措辭與命名問題，但這些詞會影響你與團隊成員對程式碼的理解。

例如，看看下面這個函式：

```python
from typing import Optional


def say_hi(name: Optional[str]):
    print(f"Hey {name}!")
```

參數 `name` 被標註為 `Optional[str]`，但它並不是可選的；你不能在沒有該參數的情況下呼叫這個函式：

```Python

    )


@pytest.mark.parametrize(
    "path",
    ["/optional-str", "/model-optional-str"],
)
def test_optional_str_missing(path: str):
    client = TestClient(app)
    response = client.get(path)
    assert response.status_code == 200
    assert response.json() == {"p": None}


@pytest.mark.parametrize(
    "path",
    ["/optional-str", "/model-optional-str"],
)
def test_optional_str(path: str):

			Optional:    true,
			Type:        "string",
			Sensitive:   false,
		},
		config.HelpKV{
			Key:         LookupBindDN,
			Description: `DN for LDAP read-only service account used to perform DN and group lookups` + defaultHelpPostfix(LookupBindDN),
			Optional:    true,
			Type:        "string",
			Sensitive:   true,
		},
		config.HelpKV{

@pytest.mark.parametrize(
    "path",
    ["/optional-str", "/model-optional-str"],
)
def test_optional_str_missing_empty_dict(path: str):
    client = TestClient(app)
    response = client.post(path, json={})
    assert response.status_code == 200, response.text
    assert response.json() == {"p": None}


@pytest.mark.parametrize(
    "path",
    ["/optional-str", "/model-optional-str"],
)
def test_optional_str(path: str):

     * @return an {@link Optional} containing the list of profile names to activate, or empty if not specified
     */
    @Nonnull
    Optional<List<String>> activatedProfiles();

    /**
     * Indicates whether Maven should suppress SNAPSHOT updates.
     *
     * @return an {@link Optional} containing true if SNAPSHOT updates should be suppressed, false if not, or empty if not specified
     */
    @Nonnull

        for (O option : options) {
            Optional<T> o = getter.apply(option);
            if (o.isPresent()) {
                return o;
            }
        }
        return Optional.empty();
    }

    protected Optional<List<String>> collectListIfPresentOrEmpty(Function<O, Optional<List<String>>> getter) {
        int had = 0;
        ArrayList<String> items = new ArrayList<>();

    /**
     * @param project The project to look for test Java resources.
     * @return An Optional that contains the Java test SourceSet if it exists.
     */
    public static Optional<SourceSet> getJavaTestSourceSet(Project project) {
        return project.getExtensions().findByName("java") == null
            ? Optional.empty()
            : Optional.ofNullable(getJavaSourceSets(project).findByName(SourceSet.TEST_SOURCE_SET_NAME));
    }

			Optional:    true,
			Type:        "string",
		},
		config.HelpKV{
			Key:         ClaimName,
			Description: `JWT canned policy claim name` + defaultHelpPostfix(ClaimName),
			Optional:    true,
			Type:        "string",
		},
		config.HelpKV{
			Key:         Scopes,

            this.scope = scope;
            return this;
        }

        public DependencyCoordinatesFactoryRequestBuilder optional(boolean optional) {
            this.optional = optional;
            return this;
        }

        public DependencyCoordinatesFactoryRequestBuilder exclusions(Collection<Exclusion> exclusions) {
            if (exclusions != null) {

    }


@pytest.mark.parametrize(
    "path",
    ["/optional-str", "/model-optional-str"],
)
def test_optional_str_missing(path: str):
    client = TestClient(app)
    response = client.post(path)
    assert response.status_code == 200
    assert response.json() == {"p": None}


@pytest.mark.parametrize(
    "path",
    ["/optional-str", "/model-optional-str"],
)
def test_optional_str(path: str):