处理 Python 事件循环关闭，无异常

#! /usr/bin/env python3from asyncio import gather, get_event_loop, sleep, Eventfrom signal import SIGINT, SIGTERMdef shutdown_signaled():    print('Shutdown requested.')    shutdown.set()async def small_work(shutdown):    while not shutdown.is_set():        await sleep(0.5)        print('Small work is done!')    print('Exited small work.')async def big_work(shutdown):    while not shutdown.is_set():        await sleep(5)        print('Big work is done!!!')    print('Exited big work.')# when this event is set the application is ready to shutdownshutdown = Event()# setting up our own handler for Ctrl+C and SIGTERM (sent with kill)# by setting this handler running tasks will not get an exception thrown at themevent_loop = get_event_loop()event_loop.add_signal_handler(SIGINT, shutdown_signaled)event_loop.add_signal_handler(SIGTERM, shutdown_signaled)# combining our two tasks as onecombined_tasks = gather(small_work(shutdown), big_work(shutdown))# run our tasks and blockevent_loop.run_until_complete(combined_tasks)