from typing import Annotated, Union

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: Union[str, None] = None, skip: int = 0, limit: int = 100):
        self.q = q
        self.skip = skip
        self.limit = limit


@app.get("/items/")

from datetime import datetime, time, timedelta
from typing import Union
from uuid import UUID

from fastapi import Body, FastAPI

app = FastAPI()


@app.put("/items/{item_id}")
async def read_items(
    item_id: UUID,
    start_datetime: datetime = Body(),
    end_datetime: datetime = Body(),
    process_after: timedelta = Body(),
    repeat_at: Union[time, None] = Body(default=None),
):

* 만약 매개변수가 **Pydantic 모델** 타입으로 선언되어 있으면, 요청 **본문**으로 해석될 것입니다.

!!! note "참고"
    FastAPI는 `q`의 값이 필요없음을 알게 될 것입니다. 기본 값이 `= None`이기 때문입니다.

    `Union[str, None]`에 있는 `Union`은 FastAPI에 의해 사용된 것이 아니지만, 편집기로 하여금 더 나은 지원과 에러 탐지를 지원할 것입니다.

## Pydantic없이

        @app.get("/query_example/")
        def query_example(
            data: Union[str, None] = Query(
                default=None,
                example="query1",
            ),
        ):
            return data

    @app.get("/query_examples/")
    def query_examples(
        data: Union[str, None] = Query(
            default=None,
            examples=["query1", "query2"],
        ),

```Python
q: str
```

вместо:

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

Но у нас query-параметр определён как `Query`. Например:

=== "Annotated"

    ```Python
    q: Annotated[Union[str, None], Query(min_length=3)] = None
    ```

=== "без Annotated"

    ```Python
    q: Union[str, None] = Query(default=None, min_length=3)
    ```

```Python
q: str
```

statt:

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

Aber jetzt deklarieren wir den Parameter mit `Query`, wie in:

=== "Annotiert"

    ```Python
    q: Annotated[Union[str, None], Query(min_length=3)] = None
    ```

=== "Nicht annotiert"

    ```Python
    q: Union[str, None] = Query(default=None, min_length=3)
    ```

```

由于我们必须用 `Query(default=None)` 替换默认值 `None`，`Query` 的第一个参数同样也是用于定义默认值。

所以：

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

...使得参数可选，等同于：

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

但是 `Query` 显式地将其声明为查询参数。

然后，我们可以将更多的参数传递给 `Query`。在本例中，适用于字符串的 `max_length` 参数：

```Python
q: Union[str, None] = Query(default=None, max_length=50)
```

将会校验数据，在数据无效时展示清晰的错误信息，并在 OpenAPI 模式的*路径操作*中记录该参​​数。

### Hozd létre

* Hozz létre a `main.py` fájlt a következő tartalommal:

```Python
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@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}
```

<details markdown="1">

from pydantic import BaseModel
from typing import Union

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}

## উদাহরণ

### তৈরি

- `main.py` নামে একটি ফাইল তৈরি করুন:

```Python
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@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}
```

<details markdown="1">