RuntimeError：异步 apscheduler 中的线程中没有当前事件循环

Question

我有一个异步函数，需要每 N 分钟运行一次 apscheduller。下面有一段python代码

URL_LIST = ['<url1>',
            '<url2>',
            '<url2>',
            ]

def demo_async(urls):
    """Fetch list of web pages asynchronously."""
    loop = asyncio.get_event_loop() # event loop
    future = asyncio.ensure_future(fetch_all(urls)) # tasks to do
    loop.run_until_complete(future) # loop until done

async def fetch_all(urls):
    tasks = [] # dictionary of start times for each url
    async with ClientSession() as session:
        for url in urls:
            task = asyncio.ensure_future(fetch(url, session))
            tasks.append(task) # create list of tasks
        _ = await asyncio.gather(*tasks) # gather task responses

async def fetch(url, session):
    """Fetch a url, using specified ClientSession."""
    async with session.get(url) as response:
        resp = await response.read()
        print(resp)

if __name__ == '__main__':
    scheduler = AsyncIOScheduler()
    scheduler.add_job(demo_async, args=[URL_LIST], trigger='interval', seconds=15)
    scheduler.start()
    print('Press Ctrl+{0} to exit'.format('Break' if os.name == 'nt' else 'C'))

    # Execution will block here until Ctrl+C (Ctrl+Break on Windows) is pressed.
    try:
        asyncio.get_event_loop().run_forever()
    except (KeyboardInterrupt, SystemExit):
        pass

但是当我尝试运行它时，我有下一个错误信息

Job "demo_async (trigger: interval[0:00:15], next run at: 2017-10-12 18:21:12 +04)" raised an exception.....
..........\lib\asyncio\events.py", line 584, in get_event_loop
    % threading.current_thread().name)
RuntimeError: There is no current event loop in thread '<concurrent.futures.thread.ThreadPoolExecutor object at 0x0356B150>_0'.

你能帮我解决这个问题吗？ Python 3.6，APScheduler 3.3.1，

原文由 Valera Shutylev 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

只需将 fetch_all scheduler.add_job() 直接传递给 --- 即可。 asyncio 调度程序支持协程函数作为作业目标。

如果目标可调用对象 不是 协程函数，它将在工作线程中运行（由于历史原因），因此会出现异常。

原文由 Alex Grönholm 发布，翻译遵循 CC BY-SA 3.0 许可协议

Answer 2

在你的 def demo_async(urls) 中，尝试替换：

 loop = asyncio.get_event_loop()

和：

 loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)

原文由 prezha 发布，翻译遵循 CC BY-SA 4.0 许可协议