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(
            alias="item-query",
            title="Query string",
            description="Query string for the items to search in the database that have a good match",
            min_length=3,
            max_length=50,

像下面这样：

```
http://127.0.0.1:8000/items/?item-query=foobaritems
```

但是 `item-query` 不是一个有效的 Python 变量名称。

最接近的有效名称是 `item_query`。

但是你仍然要求它在 URL 中必须是 `item-query`...

这时你可以用 `alias` 参数声明一个别名，该别名将用于在 URL 中查找查询参数值：

```Python hl_lines="9"
{!../../../docs_src/query_params_str_validations/tutorial009.py!}
```

## 弃用参数

现在假设你不再喜欢此参数。

from fastapi import FastAPI, Path, Query

app = FastAPI()


@app.get("/items/{item_id}")
async def read_items(
    item_id: int = Path(title="The ID of the item to get"),
    q: str | None = Query(default=None, alias="item-query"),
):
    results = {"item_id": item_id}
    if q:
        results.update({"q": q})

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(alias="item-query")] = None):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

from fastapi import FastAPI, Path, Query

app = FastAPI()


@app.get("/items/{item_id}")
async def read_items(
    item_id: int = Path(title="The ID of the item to get"),
    q: Union[str, None] = Query(default=None, alias="item-query"),
):
    results = {"item_id": item_id}
    if q:
        results.update({"q": q})

from typing import Annotated, Union

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(
    q: Annotated[
        Union[str, None],
        Query(
            alias="item-query",
            title="Query string",
            description="Query string for the items to search in the database that have a good match",
            min_length=3,
            max_length=50,

마치 다음과 같습니다:

```
http://127.0.0.1:8000/items/?item-query=foobaritems
```

그러나 `item-query`은 유효한 파이썬 변수 이름이 아닙니다.

가장 가까운 것은 `item_query`일 겁니다.

하지만 정확히`item-query`이길 원합니다...

이럴 경우 `alias`를 선언할 수 있으며, 해당 별칭은 매개변수 값을 찾는 데 사용됩니다:

```Python hl_lines="9"
{!../../../docs_src/query_params_str_validations/tutorial009.py!}
```

## 매개변수 사용하지 않게 하기

이제는 더이상 이 매개변수를 마음에 들어하지 않는다고 가정해 봅시다.

from fastapi import FastAPI, Path, Query

app = FastAPI()


@app.get("/items/{item_id}")
async def read_items(
    item_id: Annotated[int, Path(title="The ID of the item to get")],
    q: Annotated[str | None, Query(alias="item-query")] = None,
):
    results = {"item_id": item_id}
    if q:
        results.update({"q": q})

from typing import Annotated

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(
    q: Annotated[
        str | None,
        Query(
            alias="item-query",
            title="Query string",
            description="Query string for the items to search in the database that have a good match",
            min_length=3,
            max_length=50,
            pattern="^fixedquery$",

from typing import Dict, List, Optional

from fastapi import FastAPI
from pydantic import BaseModel, Field
from starlette.testclient import TestClient

app = FastAPI()


class Item(BaseModel):
    name: str = Field(alias="aliased_name")
    price: Optional[float] = None
    owner_ids: Optional[List[int]] = None


@app.get("/items/valid", response_model=Item)
def get_valid():
    return Item(aliased_name="valid", price=1.0)