from fastapi import APIRouter, Body

router = APIRouter()


@router.post("/compute/")
def compute(a: int = Body(), b: str = Body()):

    state["/async"] = "asyncgen started"
    yield state["/async"]
    state["/async"] = "asyncgen completed"


def generator_state(state: Dict[str, str] = Depends(get_state)):
    state["/sync"] = "generator started"
    yield state["/sync"]
    state["/sync"] = "generator completed"


async def asyncgen_state_try(state: Dict[str, str] = Depends(get_state)):

    ```

`OAuth2PasswordRequestForm` is a class dependency that declares a form body with:

* The `username`.
* The `password`.
* An optional `scope` field as a big string, composed of strings separated by spaces.
* An optional `grant_type`.

!!! tip
    The OAuth2 spec actually *requires* a field `grant_type` with a fixed value of `password`, but `OAuth2PasswordRequestForm` doesn't enforce it.

                    },
                    "summary": "Compute",
                    "operationId": "compute_a_compute_post",
                    "requestBody": {
                        "content": {
                            "application/json": {
                                "schema": {
                                    "$ref": "#/components/schemas/Body_compute_a_compute_post"
                                }

    with TestClient(app) as client:
        note = {"text": "Foo bar", "completed": False}
        response = client.post("/notes/", json=note)
        assert response.status_code == 200, response.text
        data = response.json()
        assert data["text"] == note["text"]
        assert data["completed"] == note["completed"]
        assert "id" in data
        response = client.get("/notes/")

### 关于 `{**note.dict(), "id": last_record_id}`

`note` 是 Pydantic `Note` 对象：

`note.dict()` 返回包含如下数据的**字典**：

```Python
{
    "text": "Some note",
    "completed": False,
}
```

但它不包含 `id` 字段。

因此要新建一个包含 `note.dict()` 键值对的**字典**：

```Python
{**note.dict()}
```

`**note.dict()` 直接**解包**键值对， 因此，`{**note.dict()}` 是 `note.dict()` 的副本。

    sqlalchemy.Column("completed", sqlalchemy.Boolean),
)


engine = sqlalchemy.create_engine(
    DATABASE_URL, connect_args={"check_same_thread": False}
)
metadata.create_all(engine)


class NoteIn(BaseModel):
    text: str
    completed: bool


class Note(BaseModel):
    id: int
    text: str
    completed: bool


app = FastAPI()

* Hinter jeder Anwendung, die Sie auf Ihrem Computer ausführen, steckt ein Prozess, jedes laufende Programm, jedes Fenster usw. Und normalerweise laufen viele Prozesse **gleichzeitig**, während ein Computer eingeschaltet ist.
* Es können **mehrere Prozesse** desselben **Programms** gleichzeitig ausgeführt werden.

You can add more than one event handler function.

And your application won't start receiving requests until all the `startup` event handlers have completed.

### `shutdown` event

To add a function that should be run when the application is shutting down, declare it with the event `"shutdown"`:

```Python hl_lines="6"
{!../../../docs_src/events/tutorial002.py!}

The API docs use **Swagger UI** and **ReDoc**, and each of those need some JavaScript and CSS files.

By default, those files are served from a <abbr title="Content Delivery Network: A service, normally composed of several servers, that provides static files, like JavaScript and CSS. It's commonly used to serve those files from the server closer to the client, improving performance.">CDN</abbr>.