from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: Union[bool, None] = None


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}


@app.put("/items/{item_id}")

{!../../docs_src/python_types/tutorial009.py!}
```

`str` yerine `Optional[str]` kullanmak editorün bu değerin her zaman `str` tipinde değil bazen `None` tipinde de olabileceğini belirtir ve hataları tespit etmemizde yardımcı olur.

#### Generic tipler

Köşeli parantez içinde tip parametreleri alan bu türler, örneğin:

* `List`
* `Tuple`
* `Set`
* `Dict`
* `Optional`
* ...and others.

        String str = result.toString();
        assertNotNull(str);
        assertTrue(str.contains("SearchResult"));
        assertTrue(str.contains("documentList="));
        assertTrue(str.contains("allRecordCount=100"));
        assertTrue(str.contains("allRecordCountRelation=eq"));
        assertTrue(str.contains("queryTime=50"));
        assertTrue(str.contains("partialResults=true"));

    AtomicInteger deliveries = new AtomicInteger();
    EventBus bus = new EventBus();
    bus.register(
        new Object() {
          @Subscribe
          public void accept(String str) {
            holder.set(str);
            deliveries.incrementAndGet();
          }
        });

    String EVENT = "Hello!";
    bus.post(EVENT);

    assertEquals("Only one event should be delivered.", 1, deliveries.get());

```Python hl_lines="1  4"
{!../../docs_src/python_types/tutorial009.py!}
```

O uso de `Optional[str]` em vez de apenas `str` permitirá que o editor o ajude a detectar erros, onde você pode estar assumindo que um valor é sempre um `str`, quando na verdade também pode ser `None`.

`Optional[Something]` é na verdade um atalho para `Union[Something, None]`, eles são equivalentes.

Isso também significa que no Python 3.10, você pode utilizar `Something | None`:

    public void test_additionalCoverage() {
        int a = 5;
        int b = 10;
        int sum = a + b;
        assertEquals(15, sum);

        String str = "Hello";
        assertTrue(str.startsWith("H"));
        assertTrue(str.endsWith("o"));
        assertEquals(5, str.length());
    }

    public void test_additionalCoverage() {
        int a = 5;
        int b = 10;
        int sum = a + b;
        assertEquals(15, sum);

        String str = "Hello";
        assertTrue(str.startsWith("H"));
        assertTrue(str.endsWith("o"));
        assertEquals(5, str.length());
    }

    public void test_additionalCoverage() {
        int a = 5;
        int b = 10;
        int sum = a + b;
        assertEquals(15, sum);

        String str = "Hello";
        assertTrue(str.startsWith("H"));
        assertTrue(str.endsWith("o"));
        assertEquals(5, str.length());
    }

    public void test_additionalCoverage() {
        int a = 5;
        int b = 10;
        int sum = a + b;
        assertEquals(15, sum);

        String str = "Hello";
        assertTrue(str.startsWith("H"));
        assertTrue(str.endsWith("o"));
        assertEquals(5, str.length());
    }

    public void test_additionalCoverage() {
        int a = 5;
        int b = 10;
        int sum = a + b;
        assertEquals(15, sum);

        String str = "Hello";
        assertTrue(str.startsWith("H"));
        assertTrue(str.endsWith("o"));
        assertEquals(5, str.length());
    }