[Python-Dev] PEP 492: async/await in Python; version 5 (original) (raw)

Paul Moore p.f.moore at gmail.com
Tue May 5 23:54:16 CEST 2015

On 5 May 2015 at 22:38, Yury Selivanov <yselivanov.ml at gmail.com> wrote:

n 2015-05-05 5:01 PM, Paul Moore wrote:

On 5 May 2015 at 21:00, Yury Selivanov <yselivanov.ml at gmail.com> wrote:

On 2015-05-05 3:40 PM, Jim J. Jewett wrote:

On Tue May 5 18:29:44 CEST 2015, Yury Selivanov posted an updated PEP492. Where are the following over-simplifications wrong? (1) The PEP is intended for use (almost exclusively) with asychronous IO and a scheduler such as the asynchio event loop. Yes. You can also use it for UI loops. Basically, anything that can call your code asynchronously. Given that the stdlib doesn't provide an example of such a UI loop, what would a 3rd party module need to implement to provide such a thing? Can any of the non-IO related parts of asyncio be reused for the purpose, or must the 3rd party module implement everything from scratch? The idea is that you integrate processing of UI events to your event loop of choice. For instance, Twisted has integration for QT and other libraries [1]. This way you can easily combine async network (or OS) calls with your UI logic to avoid "callback hell".

We seem to be talking at cross purposes. You say the PEP is not exclusively intended for use with asyncio. You mention UI loops, but when asked how to implement such a loop, you say that I integrate UI events into my event loop of choice. But what options do I have for "my event loop of choice"? Please provide a concrete example that isn't asyncio. Can I use PEP 492 with Twisted (I doubt it, as Twisted doesn't use yield from, which is Python 3.x only)? I contend that there is no concrete example that currently exists, so I'm asking what I'd need to do to write one. You pointed at qamash, but that seems to be subclassing asyncio, so isn't "something that isn't asyncio".

Note that I don't have a problem with there being no existing implementation other than asyncio. I'd just like it if we could be clear over exactly what we mean when we say "the PEP is not tied to asyncio". It feels like the truth currently is "you can write your own async framework that uses the new features introduced by the PEP". I fully expect that if there's a need for async frameworks that aren't fundamentally IO multiplexors, then it'll get easier to write them over time (the main problem right now is a lack of good tutorial examples of how to do so). But at the moment, asyncio seems to be the only game in town (and I can imagine that it'll always be the main IO multiplexor, unless existing frameworks like Twisted choose to compete rather than integrate).

Paul

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