Например, вы можете объявить, что значение может быть `str` или `None`:

```python
from typing import Union


def say_hi(name: Union[str, None]):
        print(f"Hi {name}!")
```

В `typing` также есть сокращение, чтобы объявить, что значение может быть `None`, — `Optional`.

Вот совет с моей очень субъективной точки зрения:

- 🚨 Избегайте использования `Optional[SomeType]`

    Assertions.assertTrue(pin.matchesCertificate(certA1.certificate))
    Assertions.assertFalse(pin.matchesCertificate(certB1.certificate))
  }

  @Test
  fun testMatchesSha1() {
    val pin = CertificatePinner.Pin("example.com", certC1Sha1Pin)
    Assertions.assertTrue(pin.matchesCertificate(certC1.certificate))
    Assertions.assertFalse(pin.matchesCertificate(certB1.certificate))

Örneğin, bir şeyin `str` ya da `None` olabileceğini şöyle belirtebilirsiniz:

```python
from typing import Union


def say_hi(name: Union[str, None]):
        print(f"Hi {name}!")
```

`typing`, bir şeyin `None` olabileceğini belirtmek için `Optional` ile bir kısayol da sunar.

Benim oldukça öznel bakış açıma göre küçük bir ipucu:

- 🚨 `Optional[SomeType]` kullanmaktan kaçının

	c <- 0
}

func main() {
	go f()
	<-c
	print(a)
}
</pre>

<p>
is guaranteed to print <code>"hello, world"</code>.  The write to <code>a</code>
is sequenced before the send on <code>c</code>, which is synchronized before
the corresponding receive on <code>c</code> completes, which is sequenced before
the <code>print</code>.
</p>

<p class="rule">

Par exemple, vous pourriez déclarer que quelque chose peut être un `str` ou `None` :

```python
from typing import Union


def say_hi(name: Union[str, None]):
        print(f"Hi {name}!")
```

`typing` propose également un raccourci pour déclarer que quelque chose peut être `None`, avec `Optional`.

Voici un conseil issu de mon point de vue très subjectif :

@app.exception_handler(StarletteHTTPException)
async def custom_http_exception_handler(request, exc):
    print(f"OMG! An HTTP error!: {repr(exc)}")
    return await http_exception_handler(request, exc)


@app.exception_handler(RequestValidationError)
async def validation_exception_handler(request, exc):
    print(f"OMG! The client sent invalid data!: {exc}")
    return await request_validation_exception_handler(request, exc)

<<breaking-changes>>.
endif::[]
<% if (priorVersions.size() > 0) { %>
// Add previous release to the list
Other versions:

<%
print priorVersions.join("\n| ")
print "\n"
}

if (notableHighlights.empty == false) { %>
// tag::notable-highlights[]
<% for (highlight in notableHighlights) { %>
[discrete]
[[${ highlight.anchor }]]
=== ${highlight.title}

external_data = {
    "id": "123",
    "signup_ts": "2017-06-01 12:22",
    "friends": [1, "2", b"3"],
}
user = User(**external_data)
print(user)
# > User id=123 name='John Doe' signup_ts=datetime.datetime(2017, 6, 1, 12, 22) friends=[1, 2, 3]
print(user.id)

                    if (r < 0.333) {
                        f.exists();
                        //                      System.out.print('e');
                    } else if (r < 0.667) {
                        d.listFiles();
                        //                      System.out.print('l');
                    } else if (r < 1.0) {
                        final InputStream in = f.getInputStream();

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

参数 `name` 被定义为 `Optional[str]`，但它并不是“可选”的，你不能不传这个参数就调用函数：

```Python
say_hi()  # 哎呀，这会报错！😱
```

参数 `name` 仍然是必填的（不是“可选”），因为它没有默认值。不过，`name` 接受 `None` 作为取值：

```Python
say_hi(name=None)  # 这样可以，None 是有效的 🎉
```

好消息是，在大多数情况下，你可以直接使用 `|` 来定义类型联合：

```python
def say_hi(name: str | None):
    print(f"Hey {name}!")
```