## Необов'язкові параметри

Аналогічно, Ви можете оголосити необов’язкові query параметри, встановивши для них значення за замовчуванням `None`:

{* ../../docs_src/query_params/tutorial002_py310.py hl[7] *}

У цьому випадку параметр функції `q` буде необов’язковим і за замовчуванням матиме значення `None`.

/// check | Примітка

You would have **one single `engine` object** for all your code to connect to the same database.

{* ../../docs_src/sql_databases/tutorial001_an_py310.py ln[14:18] hl[14:15,17:18] *}

Using `check_same_thread=False` allows FastAPI to use the same SQLite database in different threads. This is necessary as **one single request** could use **more than one thread** (for example in dependencies).

    "bar": {"id": "bar", "title": "Bar", "description": "The bartenders"},
}

app = FastAPI()


class Item(BaseModel):
    id: str
    title: str
    description: Union[str, None] = None


@app.get("/items/{item_id}", response_model=Item)
async def read_main(item_id: str, x_token: Annotated[str, Header()]):
    if x_token != fake_secret_token:

		{xForwardedFor, "", ""},                                                       // None
		{xRealIP, "8.8.8.8", "8.8.8.8"},                                               // Single address
		{xRealIP, "[2001:db8:cafe::17]:4711", "[2001:db8:cafe::17]"},                  // IPv6 address
		{xRealIP, "", ""},                                                             // None
		{forwarded, `for="_gazonk"`, "_gazonk"},                                       // Hostname

public class CIDetectorHelperTest {
    private static final Set<String> ALL =
            Set.of("CIRCLECI", "CI", "WORKSPACE", "GITHUB_ACTIONS", "TEAMCITY_VERSION", "TRAVIS");

    @Test
    void none() throws Exception {
        assertEquals("NONE;", runner(Map.of()));
    }

    @Test
    void generic() throws Exception {
        assertEquals(GenericCIDetector.NAME + ";", runner(Map.of("CI", "true")));
    }

    @Test

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}")
def update_item(item_id: int, item: Item):

                "loc": ["header", "x-token"],
                "msg": "Field required",
                "input": None,
            },
            {
                "type": "missing",
                "loc": ["header", "x-key"],
                "msg": "Field required",
                "input": None,
            },
        ]
    }


def test_get_invalid_one_header(client: TestClient):

    assert response.status_code == 200, response.text
    assert response.json() == {
        "name": "Foo",
        "price": 42,
        "description": None,
        "tax": None,
        "tags": [],
    }


def test_openapi_schema(client: TestClient):
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text
    assert response.json() == {

    }

    public Collection<DefaultType> types() {
        return Arrays.asList(
                // Maven types
                new DefaultType(Type.POM, Language.NONE, "pom", null, false),
                new DefaultType(Type.BOM, Language.NONE, "pom", null, false),
                new DefaultType(Type.MAVEN_PLUGIN, Language.JAVA_FAMILY, "jar", null, false, JavaPathType.CLASSES),
                // Java types

    response = client.get("/items/foo?needy=very")
    assert response.status_code == 200
    assert response.json() == {
        "item_id": "foo",
        "needy": "very",
        "skip": 0,
        "limit": None,
    }


def test_foo_no_needy(client: TestClient):
    response = client.get("/items/foo?skip=a&limit=b")
    assert response.status_code == 422
    assert response.json() == {
        "detail": [