}


app = FastAPI()


@app.get(
    "/items/{item_id}",
    response_model=Item,
    responses={**responses, 200: {"content": {"image/png": {}}}},
)
async def read_item(item_id: str, img: Union[bool, None] = None):
    if img:
        return FileResponse("image.png", media_type="image/png")
    else:

app = FastAPI()


def write_log(message: str):
    with open("log.txt", mode="a") as log:
        log.write(message)


def get_query(background_tasks: BackgroundTasks, q: str | None = None):
    if q:
        message = f"found query: {q}\n"
        background_tasks.add_task(write_log, message)
    return q


@app.post("/send-notification/{email}")
async def send_notification(

from typing_extensions import Annotated

app = FastAPI()


fake_items_db = [{"item_name": "Foo"}, {"item_name": "Bar"}, {"item_name": "Baz"}]


class CommonQueryParams:
    def __init__(self, q: Union[str, None] = None, skip: int = 0, limit: int = 100):
        self.q = q
        self.skip = skip
        self.limit = limit


@app.get("/items/")

    assert response.json() == {"name": "Wrestlers", "size": None}


@needs_py310
def test_create(client: TestClient):
    response = client.put("/items/red", json={"name": "Chillies"})
    assert response.status_code == 201, response.text

  }

  public void testToArray() {
    // need explicit type parameter to avoid javac warning!?
    List<Byte> none = Arrays.<Byte>asList();
    assertThat(Bytes.toArray(none)).isEqualTo(EMPTY);

    List<Byte> one = Arrays.asList((byte) 1);
    assertThat(Bytes.toArray(one)).isEqualTo(ARRAY1);

    byte[] array = {(byte) 0, (byte) 1, (byte) 0x55};

app = FastAPI()


def write_log(message: str):
    with open("log.txt", mode="a") as log:
        log.write(message)


def get_query(background_tasks: BackgroundTasks, q: Union[str, None] = None):
    if q:
        message = f"found query: {q}\n"
        background_tasks.add_task(write_log, message)
    return q


@app.post("/send-notification/{email}")
async def send_notification(

    assert response.json() == {"name": "Wrestlers", "size": None}


@needs_py39
def test_create(client: TestClient):
    response = client.put("/items/red", json={"name": "Chillies"})
    assert response.status_code == 201, response.text

Поскольку по умолчанию, отдельные значения интерпретируются как query-параметры, вам не нужно явно добавлять `Query`, вы можете просто сделать так:

```Python
q: Union[str, None] = None
```

Или в Python 3.10 и выше:

```Python
q: str | None = None
```

Например:

//// tab | Python 3.10+

```Python hl_lines="27"
{!> ../../docs_src/body_multiple_params/tutorial004_an_py310.py!}
```

////

    }

    /**
     * Gets the one-based index of the line containing the error.
     *
     * @return The one-based index of the line containing the error or a non-positive value if unknown.
     */
    public int getLineNumber() {
        return lineNumber;
    }

    /**
     * Gets the one-based index of the column containing the error.
     *

This is not a limitation of **FastAPI**, it's part of the HTTP protocol.

///

## Optional File Upload

You can make a file optional by using standard type annotations and setting a default value of `None`:

//// tab | Python 3.10+

```Python hl_lines="9  17"
{!> ../../docs_src/request_files/tutorial001_02_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="9  17"