from typing import Union

from fastapi import FastAPI, Query
from typing_extensions import Annotated

app = FastAPI()


@app.get("/items/")
async def read_items(
    q: Annotated[Union[str, None], Query(title="Query string", min_length=3)] = None,
):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

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

//// tab | Python 3.10+

```Python hl_lines="7"
{!> ../../docs_src/query_params/tutorial002_py310.py!}
```

////

//// tab | Python 3.8+

```Python hl_lines="9"
{!> ../../docs_src/query_params/tutorial002.py!}
```

////

In diesem Fall wird der Funktionsparameter `q` optional, und standardmäßig `None` sein.

/// check

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!}
```

////

from fastapi import Depends, FastAPI

app = FastAPI()


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


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


@app.get("/items/")

from sqlmodel import Field, Session, SQLModel, create_engine, select


class Hero(SQLModel, table=True):
    id: Union[int, None] = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    age: Union[int, None] = Field(default=None, index=True)
    secret_name: str


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

}


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/")