from typing import Union

from fastapi import FastAPI

app = FastAPI()


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

```Python hl_lines="9"
{!../../docs_src/header_params/tutorial003.py!}
```

다음과 같은 두 개의 HTTP 헤더를 전송하여 해당 *경로* 와 통신할 경우:

```
X-Token: foo
X-Token: bar
```

응답은 다음과 같습니다:

```JSON
{
    "X-Token values": [
        "bar",
        "foo"
    ]
}
```

## 요약

`Header`는 `Query`, `Path`, `Cookie`와 동일한 패턴을 사용하여 선언합니다.

label:
	JB	-4(PC) // JCS -4(PC)
	JB	label // JCS 17

// LTYPEC spec3	{ outcode($1, &$2); }
	JCS	2(PC)
	JMP	-4(PC)
	JCS	2(PC)
	JMP	label // JMP 17
	JCS	2(PC)
	JMP	foo+4(SB)
	JCS	2(PC)
	JMP	bar<>+4(SB)
	JCS	2(PC)
	JMP	bar<>+4(SB)(R11*4)
	JCS	2(PC)
	JMP	*4(SP) // JMP 4(SP)
	JCS	2(PC)
	JMP	*(R12) // JMP (R12)
	JCS	2(PC)
//	JMP	*(R12*4) // TODO: This line is silently dropped on the floor!
	JCS	2(PC)

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: str | None = Query(default=None, min_length=3, max_length=50)):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

from typing_extensions import Annotated

app = FastAPI()


@app.get("/items/")
async def read_items(q: Annotated[str, Query(min_length=3)] = ...):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

from typing_extensions import Annotated

app = FastAPI()


@app.get("/items/")
async def read_items(q: Annotated[str, Query(min_length=3)] = "fixedquery"):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

{!../../docs_src/query_params_str_validations/tutorial011.py!}
```

然后，输入如下网址：

```
http://localhost:8000/items/?q=foo&q=bar
```

你会在*路径操作函数*的*函数参数* `q` 中以一个 Python `list` 的形式接收到*查询参数* `q` 的多个值（`foo` 和 `bar`）。

因此，该 URL 的响应将会是：

```JSON
{
  "q": [
    "foo",
    "bar"
  ]
}
```

/// tip

要声明类型为 `list` 的查询参数，如上例所示，你需要显式地使用 `Query`，否则该参数将被解释为请求体。

///

        self.fixed_content = fixed_content

    def __call__(self, q: str = ""):
        if q:
            return self.fixed_content in q
        return False


checker = FixedContentQueryChecker("bar")


@app.get("/query-checker/")
async def read_query_check(fixed_content_included: bool = Depends(checker)):

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/")
async def read_items(commons: CommonQueryParams = Depends(CommonQueryParams)):
    response = {}

            {
                "name": "Foo",
                "description": "A very nice Item",
                "price": 35.4,
                "tax": 3.2,
            },
            {
                "name": "Bar",
                "price": "35.4",
            },
            {
                "name": "Baz",
                "price": "thirty five point four",
            },
        ],
    ),
):