You will also get autocompletion for the payload to send:

<img src="/img/tutorial/generate-clients/image03.png">

!!! tip
    Notice the autocompletion for `name` and `price`, that was defined in the FastAPI application, in the `Item` model.

You will have inline errors for the data that you send:

<img src="/img/tutorial/generate-clients/image04.png">

    with pytest.raises(InternalError) as exc_info:
        client.get("/items/portal-gun")
    assert (
        exc_info.value.args[0] == "The portal gun is too dangerous to be owned by Rick"
    )


def test_internal_server_error():
    from docs_src.dependencies.tutorial008d_an import app

    client = TestClient(app, raise_server_exceptions=False)
    response = client.get("/items/portal-gun")

!!! info
    Keep in mind that dataclasses can't do everything Pydantic models can do.

    So, you might still need to use Pydantic models.

    But if you have a bunch of dataclasses laying around, this is a nice trick to use them to power a web API using FastAPI. 🤓

## Dataclasses in `response_model`

You can also use `dataclasses` in the `response_model` parameter:

```Python hl_lines="1  7-13  19"

    "description": "The bartenders",
    "price": 62,
    "tax": 20.2
}
```

they will be included in the response.

#### Data with the same values as the defaults

If the data has the same values as the default ones, like the item with ID `baz`:

```Python hl_lines="3  5-6"
{
    "name": "Baz",
    "description": None,
    "price": 50.2,
    "tax": 10.5,
    "tags": []
}
```

```Python hl_lines="30-35"
{!../../../docs_src/body_updates/tutorial001.py!}
```

`PUT` 用于接收替换现有数据的数据。

### 关于更新数据的警告

用 `PUT` 把数据项 `bar` 更新为以下内容时：

```Python
{
    "name": "Barz",
    "price": 3,
    "description": None,
}
```

因为上述数据未包含已存储的属性 `"tax": 20.2`，新的输入模型会把 `"tax": 10.5` 作为默认值。

因此，本次操作把 `tax` 的值「更新」为 `10.5`。

## 用 `PATCH` 进行部分更新

            "X-Token": "fake-super-secret-token",
            "X-Key": "fake-super-secret-key",
        },
    )
    assert response.status_code == 200, response.text
    assert response.json() == [{"username": "Rick"}, {"username": "Morty"}]


def test_openapi_schema():
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text
    assert response.json() == {
        "openapi": "3.1.0",

![editor support](https://fastapi.tiangolo.com/img/pycharm-completion.png)

Bạn sẽ có được auto-completion trong code, thậm chí trước đó là không thể. Như trong ví dụ, khóa `price` bên trong một JSON (đó có thể được lồng nhau) đến từ một request.

Không còn nhập sai tên khóa, quay đi quay lại giữa các tài liệu hoặc cuộn lên cuộn xuống để tìm xem cuối cùng bạn đã sử dụng `username` hay `user_name`.

    return client


def test_users_token_jessica(client: TestClient):
    response = client.get("/users?token=jessica")
    assert response.status_code == 200
    assert response.json() == [{"username": "Rick"}, {"username": "Morty"}]


def test_users_with_no_token(client: TestClient):
    response = client.get("/users")
    assert response.status_code == 422
    assert response.json() == IsDict(
        {

    return client


@needs_py39
def test_users_token_jessica(client: TestClient):
    response = client.get("/users?token=jessica")
    assert response.status_code == 200
    assert response.json() == [{"username": "Rick"}, {"username": "Morty"}]


@needs_py39
def test_users_with_no_token(client: TestClient):
    response = client.get("/users")
    assert response.status_code == 422
    assert response.json() == IsDict(
        {

    name: str
    date: datetime
    price: Optional[float] = None
    owner_ids: Optional[List[int]] = None


@app.get("/items/valid", response_model=Item)
def get_valid():
    return {"name": "valid", "date": datetime(2021, 7, 26), "price": 1.0}


@app.get("/items/object", response_model=Item)
def get_object():
    return Item(
        name="object", date=datetime(2021, 7, 26), price=1.0, owner_ids=[1, 2, 3]
    )