media_type = "application/x-override"


app = FastAPI(default_response_class=ORJSONResponse)
router_a = APIRouter()
router_a_a = APIRouter()
router_a_b_override = APIRouter()  # Overrides default class
router_b_override = APIRouter()  # Overrides default class
router_b_a = APIRouter()
router_b_a_c_override = APIRouter()  # Overrides default class again


@app.get("/")
def get_root():

app = FastAPI()
router_a = APIRouter()
router_a_a = APIRouter()
router_a_b_override = APIRouter()  # Overrides default class
router_b_override = APIRouter()  # Overrides default class
router_b_a = APIRouter()
router_b_a_c_override = APIRouter()  # Overrides default class again


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

Sebastián Ramírez <******@****.***> 1688149516 +0200

    ```

## Required query parameters

When you declare a default value for non-path parameters (for now, we have only seen query parameters), then it is not required.

If you don't want to add a specific value but just make it optional, set the default as `None`.

But when you want to make a query parameter required, you can just not declare any default value:

```Python hl_lines="6-7"

        '"dom_id": "#swagger-ui"' in response.text
    ), "default configs should be preserved"
    assert "presets: [" in response.text, "default configs should be preserved"
    assert (
        "SwaggerUIBundle.presets.apis," in response.text
    ), "default configs should be preserved"
    assert (
        "SwaggerUIBundle.SwaggerUIStandalonePreset" in response.text
    ), "default configs should be preserved"
    assert (

As in this case (without using `Annotated`) we have to replace the default value `None` in the function with `Query()`, we now need to set the default value with the parameter `Query(default=None)`, it serves the same purpose of defining that default value (at least for FastAPI).

So:

```Python
q: Union[str, None] = Query(default=None)
```

...makes the parameter optional, with a default value of `None`, the same as:

```Python

        UploadFile._validate("not a Starlette UploadFile", {})


def test_default_placeholder_equals():
    placeholder_1 = Default("a")
    placeholder_2 = Default("a")
    assert placeholder_1 == placeholder_2
    assert placeholder_1.value == placeholder_2.value


def test_default_placeholder_bool():
    placeholder_a = Default("a")
    placeholder_b = Default("")
    assert placeholder_a
    assert not placeholder_b

        "5xx": {"description": "Error with range, lower"},
        "default": {"description": "A default response"},
    },
)
async def c():
    return "c"


@router.get(
    "/d",
    responses={
        "400": {"description": "Error with str"},
        "5XX": {"model": ResponseModel},
        "default": {"model": ResponseModel},
    },
)
async def d():
    return "d"

        @app.get("/items/")
        def read_items(q: List[Item] = Query(default=None)):
            pass  # pragma: no cover


def test_invalid_tuple():
    with pytest.raises(AssertionError):
        app = FastAPI()

        class Item(BaseModel):
            title: str

        @app.get("/items/")
        def read_items(q: Tuple[Item, Item] = Query(default=None)):
            pass  # pragma: no cover

app = FastAPI()


@app.get("/items/")
def read_items(q: Optional[str] = Param(default=None)):  # type: ignore
    return {"q": q}


client = TestClient(app)


def test_default_param_query_none():
    response = client.get("/items/")
    assert response.status_code == 200, response.text
    assert response.json() == {"q": None}


def test_default_param_query():
    response = client.get("/items/?q=foo")