Periodic execution with asyncio

[Terry Reedy]

On 11/22/2013 7:00 PM, Terry Reedy wrote:
> On 11/22/2013 4:30 PM, Tobias M. wrote:

[snip callback versions by Tobias and me]

>> 2. How would you implement the second approach from the PEP (using a
>> coroutine) with the same interface as my PeriodicTask above?
>
> Theoretically, by Guido's rationale, that should be easier (for me, at
> least), since it would be more like the kind of Python code I already
> write.
>
>> I tried the second approach but wasn't able to come up with a solution,
>> as I was too confused by the concepts of coroutines, Tasks, etc.
>
> I will try to look at the PEP and see how it works for me.

I was initially baffled also until I managed to assemble all the needed 
pieces.

import asyncio

def f():
     print('Hello World')

@asyncio.coroutine
def g(func, interval):
     while True:
         yield from asyncio.sleep(interval)
         func()

loop = asyncio.get_event_loop()

try:
     loop.run_until_complete(asyncio.Task(g(f, 2)))
except KeyboardInterrupt:
     print('Loop stopped')

I think Guido's point is that async generator version is quite similar 
to the 'normal' synchronous version.

import time

def f():
     print('Hello World')

def h(func, interval):
     while True:
         time.sleep(interval)
         func()

try:
     h(f, 2))
except KeyboardInterrupt:
     print('Loop stopped')

-- 
Terry Jan Reedy