]

app = FastAPI()


@app.websocket("/function-scope")
async def function_scope(websocket: WebSocket, session: SessionFuncDep) -> Any:
    await websocket.accept()
    await websocket.send_json({"is_open": session.open})


@app.websocket("/request-scope")
async def request_scope(websocket: WebSocket, session: SessionRequestDep) -> Any:
    await websocket.accept()

### Dateien und Async { #files-and-async }

In den meisten Fällen sind dateiähnliche Objekte standardmäßig nicht mit async und await kompatibel.

Beispielsweise haben sie kein `await file.read()` oder `async for chunk in file`.

@app.get("/items/stream", response_class=EventSourceResponse)
async def sse_items() -> AsyncIterable[Item]:
    for item in items:
        yield item


@app.get("/items/stream-sync", response_class=EventSourceResponse)
def sse_items_sync() -> Iterable[Item]:
    yield from items


@app.get("/items/stream-no-annotation", response_class=EventSourceResponse)
async def sse_items_no_annotation():
    for item in items:

The first thing to notice, is that we are defining an async function with `yield`. This is very similar to Dependencies with `yield`.

{* ../../docs_src/events/tutorial003_py310.py hl[14:19] *}

The first part of the function, before the `yield`, will be executed **before** the application starts.

And the part after the `yield` will be executed **after** the application has finished.

### Async Context Manager { #async-context-manager }

在這個範例中因為是存在記憶體的假檔案（`io.BytesIO`），影響不大；但若是實際檔案，務必在處理完成後關閉檔案。

### 檔案與 Async { #files-and-async }

多數情況下，類檔案物件預設不相容於 async/await。

例如，它們沒有 `await file.read()`，也不支援 `async for chunk in file`。

而且在許多情況下，讀取它們會是阻塞操作（可能阻塞事件迴圈），因為資料是從磁碟或網路讀取。

/// info

上面的範例其實是例外，因為 `io.BytesIO` 物件已在記憶體中，讀取不會阻塞任何東西。

但在多數情況下，讀取檔案或類檔案物件會造成阻塞。

///

為了避免阻塞事件迴圈，你可以將路徑操作函式宣告為一般的 `def`（而非 `async def`），這樣 FastAPI 會在 threadpool worker 上執行它，避免阻塞主事件迴圈。

]


@app.get("/items/stream")
async def stream_items() -> AsyncIterable[Item]:
    for item in items:
        yield item


@app.get("/items/stream-no-async")
def stream_items_no_async() -> Iterable[Item]:
    for item in items:
        yield item


@app.get("/items/stream-no-annotation")
async def stream_items_no_annotation():
    for item in items:
        yield item

### Файлы и async { #files-and-async }

В большинстве случаев «файлоподобные» объекты по умолчанию не совместимы с async и await.

Например, у них нет `await file.read()` или `async for chunk in file`.

    )


@app.get(app.swagger_ui_oauth2_redirect_url, include_in_schema=False)
async def swagger_ui_redirect():
    return get_swagger_ui_oauth2_redirect_html()


@app.get("/redoc", include_in_schema=False)
async def redoc_html():
    return get_redoc_html(
        openapi_url=app.openapi_url,
        title=app.title + " - ReDoc",

from fastapi.testclient import TestClient

app = FastAPI()


async def common_parameters(q: str | None = None, skip: int = 0, limit: int = 100):
    return {"q": q, "skip": skip, "limit": limit}


@app.get("/items/")
async def read_items(commons: dict = Depends(common_parameters)):
    return {"message": "Hello Items!", "params": commons}


@app.get("/users/")
async def read_users(commons: dict = Depends(common_parameters)):

if TYPE_CHECKING:  # pragma: no cover
    from collections.abc import AsyncGenerator


class DummyClient:
    async def get_people(self) -> list:
        return ["John Doe", "Jane Doe"]

    async def close(self) -> None:
        pass


async def get_client() -> AsyncGenerator[DummyClient, None]:
    client = DummyClient()
    yield client
    await client.close()