python - 无法使用标准方法将 MotorCursor 对象转换为异步函数中的列表

Question

我一直在尝试让异步函数从 Python 中的电机数据库中获取数据，并获取与搜索对应的数据列表。这是获取数据和打印数据的函数：

async def do_find_by_run_name(run_name):
    """
    :param run_name: the name of a the run being searched for (string)
    :return: MotorCursor for run found
    """
    cursor = db.data_collection.find({"run_name":run_name})
    loop = asyncio.get_event_loop()
    return cursor

async def print_arr(cursor):
    for d in await cursor.to_list(length=2):
        pprint.pprint(d)

我有一个 PyQt 插槽，我想用它在按下按钮时调用 find_by_run_name 函数。这是该插槽的代码：

@pyqtSlot()
def on_find_runs_button_clicked(self):
    try:
        new_loop = asyncio.get_event_loop()
        d = new_loop.run_until_complete(server.do_find_by_run_name("default"))
        print(d)
        new_loop = asyncio.get_event_loop()
        v = new_loop.run_until_complete(server.print_arr(d))
    except Exception as err:
        try:
            raise TypeError("Again !?!")
        except:
            pass
        traceback.print_exc()

当我按下与此插槽对应的按钮时，我在终端中看到以下内容：

AsyncIOMotorCursor(<pymongo.cursor.Cursor object at 0x06F51EB0>)
Traceback (most recent call last):
  File "C:/Users/Rohan Doshi/Documents/websockets/server\GUI.py", line 93, in on_find_runs_button_clicked
    v = new_loop.run_until_complete(server.print_arr(d))
  File "C:\Users\Rohan Doshi\AppData\Local\Programs\Python\Python36-32\lib\asyncio\base_events.py", line 468, in run_until_complete
    return future.result()
  File "C:/Users/Rohan Doshi/Documents/websockets/server\server.py", line 130, in print_arr
    for d in await cursor.to_list(length=2):
RuntimeError: Task <Task pending coro=<print_arr() running at C:/Users/Rohan Doshi/Documents/websockets/server\server.py:130> cb=[_run_until_complete_cb() at C:\Users\Rohan Doshi\AppData\Local\Programs\Python\Python36-32\lib\asyncio\base_events.py:177]> got Future <Future pending> attached to a different loop

这向我表明 do_find_by_run_name 函数运行正常，但运行 print_arr 函数存在问题。

为了解决此问题，do_find_run_name 已更改为：

async def do_find_by_run_name(run_name):
    """
    :param run_name: the name of a the run being searched for (string)
    :return: MotorCursor for run found
    """
    cursor = db.data_collection.find({"run_name":run_name})
    print(cursor)
    for d in await cursor.to_list(length=2):
        pprint.pprint(d)

我将我的 PyQt 插槽更改为：

@pyqtSlot()
def on_find_runs_button_clicked(self):
    try:
        new_loop = asyncio.get_event_loop()
        future = asyncio.run_coroutine_threadsafe(
            server.do_find_by_run_name("default"),
            new_loop
        )
        assert future.result(timeout=10)
    except Exception as err:
        try:
            raise TypeError("Again !?!")
        except:
            pass
        traceback.print_exc()

进行此更改后，我看不到任何打印内容。似乎 do_find_run_name couroutine 从未执行过。

标签： pythonpyqt5python-asynciotornado-motor