On 8/20/2018 3:19 AM, Simon De Greve wrote:
Hello everyone,
I'm quite new working with asyncio and thus maybe missing some things
about it, but wouldn't it be quite easier to have some iterables to
support async for loops "natively", since asyncio is now part of the
Stdlib?
One purpose of asynchronous programming is to pause a task that is
waiting for input from an external system, so as to not waste CPU time.
As other noted, this is not an issue with iterating through in-memory
collections.
It is worth noting that 'async' and 'await' are syntax keywords for
working with coroutines (how is underdocumented) and that the asyncio
module is just one event-loop system that can drive coroutines. The
tkinter module, over 20 years old, can also.
I've tried to work with asyncio while using discord.py, and has some
struggle with an "async for" loop on a dictionary, so I had to implement
a new dict subclass that would just reimplement items(), keys() and
values() functions.
Another purpose of asynchonous programming is to keep a system
responsive, for instance, to user input by not letting a compute-bound
task tie-up a cpu indefinitely. This issue *can* apply to iterating
through sufficiently large collection in, for instance, a tkinter gui
program. But pausing iteration after *each* iteration is usually a
terrible waste of overhead. So one wants to do some number of
iterations at full speed and then pause to allow other events to be handled.
I think that it would be a cool improvement to implement some of those
in some standard way.
Occasionally pausing iteration should not be a method of the iterable or
iterator. We need instead wrapper functions. One idea is to pause
every k iterations. For user responsiveness, we want to pause for event
handling after a certain time has elapsed, say 50 milliseconds. I think
it should be possible to do this directly instead of pre-testing how
long it takes to do 1 interation.
I know how to do the above with tkinter callback loops, but I have not
yet worked out how to do so with async def coroutines.
--
Terry Jan Reedy
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