[Python-Dev] PEP 492: async/await in Python; version 4

Paul Moore p.f.moore at gmail.com
Tue May 5 23:16:46 CEST 2015

On 5 May 2015 at 21:57, Guido van Rossum <guido at python.org> wrote:
> On Tue, May 5, 2015 at 1:39 PM, Paul Moore <p.f.moore at gmail.com> wrote:
>> It's very hard to separate coroutines from asyncio, because there's no
>> other example (not even a toy one) to reason about.
> What about Greg Ewing's example?
> http://www.cosc.canterbury.ac.nz/greg.ewing/python/yield-from/yf_current/Examples/Scheduler/scheduler.txt

That doesn't cover any of the higher level abstractions like tasks or
futures (at least not by those names or with those interfaces). And I
don't see where the PEP 492 additions would fit in (OK, "replace yield
from with await" is part of it, but I don't see the rest).

We may be talking at cross purposes here. There's a lot of asyncio
that doesn't seem to me to be IO-related. Specifically the future and
task abstractions. I view those as relevant to "coroutine programming
in Python" because they are referenced in any discussion of coroutines
(you yield from a future, for example). If you see them as purely
asyncio related (and not directly usable from outside of an asyncio
context) then that may explain some of my confusion (but at the cost
of reducing the coroutine concept to something pretty trivial in the
absence of a library that independently implements these concepts).

In some ways I wish there had been an "asyncio" library that covered
the areas that are fundamentally about IO multiplexing. And a separate
library (just "async", maybe, although that's now a bad idea as it
clashes with a keyword :-)) that covered generic event loop, task and
synchronisation areas. But that's water under the bridge now.


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