Thanks Phil, now I understand! I wasn't aware of the fact that tasks are automatically attached to the event loop when they are created via their constructor. I thought I have to pass them to a run_* method explicitly.
Phil Connell <pconn...@gmail.com> schrieb: >On Sat, Nov 23, 2013 at 09:30:29PM +0100, Tobias M. wrote: >> Now putting this into a PeriodicTask class that provides a similar >interface >> like our callback version, I get: >> >> >> import asyncio >> >> class PeriodicTask2(object): >> >> def __init__(self, func, interval): >> self.func = func >> self.interval = interval >> self._loop = asyncio.get_event_loop() >> >> def start(self): >> self.loop.run_until_complete(asyncio.Task(self._run())) >> >> @asyncio.coroutine >> def _run(self): >> while True: >> yield from asyncio.sleep(self.interval) >> self.func() >> >> >> I don't know if I misunderstood anything, but as a user of this class >I am >> not able to run two task simultaneously because start() will block. >In the >> callback version I could instanciate two PeriodicTasks and run them >both at >> the same time (after a call to loop.run_forever()), which is actually >what I >> wanted to achieve with this class. > >You need to separate out creating tasks from running the event loop. > >Specifically, you should run the event loop in exactly one place, >probably at >the top level of your script. > > >A toy example: > >import asyncio > >@asyncio.coroutine >def adder(*args, delay): > yield from asyncio.sleep(delay) > print(sum(args)) > >def main(): > asyncio.Task(adder(1, 2, 3, delay=5)) > asyncio.Task(adder(10, 20, delay=3)) > > loop = asyncio.get_event_loop() > loop.run_forever() > >if __name__ == "__main__": > main() > > >$ ./python test.py >30 >6 > > >Note that run_forever() will block indefinitely (as the name suggests >:). This >is generally what you'll want for a long-running server. > >If you want do something more like: > - Spawn some tasks > - Run the event loop until they're done > - Exit > >then you'll need to use loop.run_until_complete(asyncio.gather(*tasks)) >instead. > > >HTH, >Phil
-- https://mail.python.org/mailman/listinfo/python-list
