# 响应 - 更改状态码

你可能之前已经了解到，你可以设置默认的[响应状态码](../tutorial/response-status-code.md){.internal-link target=_blank}。

但在某些情况下，你需要返回一个不同于默认值的状态码。

## 使用场景

例如，假设你想默认返回一个HTTP状态码为“OK”`200`。

但如果数据不存在，你想创建它，并返回一个HTTP状态码为“CREATED”`201`。

但你仍然希望能够使用`response_model`过滤和转换你返回的数据。

对于这些情况，你可以使用一个`Response`参数。

## 使用 `Response` 参数

你可以在你的*路径操作函数*中声明一个`Response`类型的参数（就像你可以为cookies和头部做的那样）。

然后你可以在这个*临时*响应对象中设置`status_code`。

    val response1 = client.newCall(request1).execute()
    assertThat(response1.code).isEqualTo(401)
    assertThat(response1.body.string())
      .isEqualTo("{\"error\":{\"message\":\"No auth credentials found\",\"code\":401}}")

    val request2 = request1.newBuilder().header("Authorization", "XYZ").build()
    val response2 = client.newCall(request2).execute()

# `Response` class

You can declare a parameter in a *path operation function* or dependency to be of type `Response` and then you can set data for the response like headers or cookies.

You can also use it directly to create an instance of it and return it from your *path operations*.

You can import it directly from `fastapi`:

```python
from fastapi import Response
```

        assertEquals(0, response.writeDataWireFormat(null, 0));

        // Read methods return 0 without accessing null buffer
        assertEquals(0, response.readSetupWireFormat(null, 0, 0));
        assertEquals(0, response.readParametersWireFormat(null, 0, 0));
        assertEquals(0, response.readDataWireFormat(null, 0, 0));
    }

    @Test

/*! Respond.js v1.4.2: min/max-width media query polyfill * Copyright 2013 Scott Jehl
 * Licensed under https://github.com/scottjehl/Respond/blob/master/LICENSE-MIT
 *  */

        for additional_status_code, response in self.responses.items():
            assert isinstance(response, dict), "An additional response must be a dict"
            model = response.get("model")
            if model:
                assert is_body_allowed_for_status_code(additional_status_code), (
                    f"Status code {additional_status_code} must not have a response body"
                )

async def dep0(response: Response):
    response.headers["x-level0"] = "True"


async def dep1(response: Response):
    response.headers["x-level1"] = "True"


async def dep2(response: Response):
    response.headers["x-level2"] = "True"


async def dep3(response: Response):
    response.headers["x-level3"] = "True"


async def dep4(response: Response):

    assert "redoc@2" in response.text


def test_enum_status_code_response():
    response = client.get("/enum-status-code")
    assert response.status_code == 201, response.text
    assert response.json() == "foo bar"


def test_openapi_schema():
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text

def test_a():
    response = client.get("/a")
    assert response.status_code == 200, response.text
    assert response.json() == "a"


def test_b():
    response = client.get("/b")
    assert response.status_code == 200, response.text
    assert response.json() == "b"


def test_c():
    response = client.get("/c")
    assert response.status_code == 200, response.text
    assert response.json() == "c"

# Custom Response - HTML, Stream, File, others { #custom-response-html-stream-file-others }

By default, **FastAPI** will return the responses using `JSONResponse`.

You can override it by returning a `Response` directly as seen in [Return a Response directly](response-directly.md){.internal-link target=_blank}.