1__all__ = 'run', 2 3from . import coroutines 4from . import events 5from . import tasks 6 7 8def run(main, *, debug=False): 9 """Run a coroutine. 10 11 This function runs the passed coroutine, taking care of 12 managing the asyncio event loop and finalizing asynchronous 13 generators. 14 15 This function cannot be called when another asyncio event loop is 16 running in the same thread. 17 18 If debug is True, the event loop will be run in debug mode. 19 20 This function always creates a new event loop and closes it at the end. 21 It should be used as a main entry point for asyncio programs, and should 22 ideally only be called once. 23 24 Example: 25 26 async def main(): 27 await asyncio.sleep(1) 28 print('hello') 29 30 asyncio.run(main()) 31 """ 32 if events._get_running_loop() is not None: 33 raise RuntimeError( 34 "asyncio.run() cannot be called from a running event loop") 35 36 if not coroutines.iscoroutine(main): 37 raise ValueError("a coroutine was expected, got {!r}".format(main)) 38 39 loop = events.new_event_loop() 40 try: 41 events.set_event_loop(loop) 42 loop.set_debug(debug) 43 return loop.run_until_complete(main) 44 finally: 45 try: 46 _cancel_all_tasks(loop) 47 loop.run_until_complete(loop.shutdown_asyncgens()) 48 finally: 49 events.set_event_loop(None) 50 loop.close() 51 52 53def _cancel_all_tasks(loop): 54 to_cancel = tasks.all_tasks(loop) 55 if not to_cancel: 56 return 57 58 for task in to_cancel: 59 task.cancel() 60 61 loop.run_until_complete( 62 tasks.gather(*to_cancel, loop=loop, return_exceptions=True)) 63 64 for task in to_cancel: 65 if task.cancelled(): 66 continue 67 if task.exception() is not None: 68 loop.call_exception_handler({ 69 'message': 'unhandled exception during asyncio.run() shutdown', 70 'exception': task.exception(), 71 'task': task, 72 }) 73