Path: csiph.com!eternal-september.org!feeder.eternal-september.org!mx02.eternal-september.org!.POSTED!not-for-mail
From: Marko Rauhamaa <marko@pacujo.net>
Newsgroups: comp.lang.python
Subject: Re: asyncio - run coroutine in the background
Date: Tue, 16 Feb 2016 19:14:18 +0200
Organization: A noiseless patient Spider
Lines: 50
Message-ID: <87mvr0k26t.fsf@elektro.pacujo.net>
References: <mailman.131.1455518141.22075.python-list@python.org> <8737sumpjl.fsf@elektro.pacujo.net> <mailman.132.1455520607.22075.python-list@python.org> <87h9ha8lt0.fsf@jester.gateway.pace.com> <CAPTjJmoWUDfcOe3OCaMK7=zDtW3QzS+7hqUG6DoYZ2AbqzJBUw@mail.gmail.com> <mailman.166.1455628969.22075.python-list@python.org> <87d1rwpwo2.fsf@elektro.pacujo.net> <56c33d7e$0$1587$c3e8da3$5496439d@news.astraweb.com>
Mime-Version: 1.0
Content-Type: text/plain
Injection-Info: mx02.eternal-september.org; posting-host="b7cb1518d23ec19d482dcc9c31d30fdd"; logging-data="30835"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1/tIX1oS+N+L+S0S2BgNhM+"
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux)
Cancel-Lock: sha1:kz0XJZOjGlq0cVkd8l89/hbucTw= sha1:WPU9XH0jxTrlp8WbQoFPx7pfNcQ=
Xref: csiph.com comp.lang.python:103020

Steven D'Aprano <steve@pearwood.info>:

> On Wed, 17 Feb 2016 01:17 am, Marko Rauhamaa wrote:
>
>> Ok, yes, but those "background tasks" monopolize the CPU once they are
>> scheduled to run.
>
> Can you show some code demonstrating this?

Sure:

========================================================================
#!/usr/bin/env python3

import asyncio, time

def main():
    asyncio.get_event_loop().run_until_complete(asyncio.wait([
        background_task(),
        looping_task() ]))

@asyncio.coroutine
def looping_task():
    while True:
        yield from asyncio.sleep(1)
        print(int(time.time()))

@asyncio.coroutine
def background_task():
    yield from asyncio.sleep(4)
    t = time.time()
    while time.time() - t < 10:
        pass

if __name__ == '__main__':
    main()
========================================================================

which prints:

   1455642629
   1455642630
   1455642631
   1455642642                <============== gap
   1455642643
   1455642644
   1455642645


Marko