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

Yury Selivanov yselivanov.ml at gmail.com
Thu May 7 20:01:48 CEST 2015

On 2015-05-07 1:42 PM, Guido van Rossum wrote:

On Tue, May 5, 2015 at 3:36 PM, Rajiv Kumar <rajiv.kumar at gmail.com> wrote:

I wrote a little example[1] that has a bare-bones implementation of Go style channels via a custom event loop. I used it to translate the prime sieve example from Go[2] almost directly to Python. The code uses "message = await channel.receive()" to mimic Go's "message <- channel". Instead of using "go func()" to fire off a goroutine, I add the PEP492 coroutine to my simple event loop. Cool example! It's not an efficient implementation - really just a proof of concept that you can use async/await in your own code without any reference to asyncio. I ended up writing it as I was thinking about how PEP 342 style coroutines might look like in an async/await world.

In the course of writing this, I did find that it would be useful to have the PEP document how event loops should advance the coroutines (via .send(None) for example). It would also be helpful to have the semantics of how await interacts with different kinds of awaitables documented. I had to play with Yury's implementation to see what it does if the await just returns iter([1,2,3]) for example. I've found this too. :-) Yury, perhaps you could show a brief example in the PEP of how to "drive" a coroutine from e.g. main()?

OK, will do!

Thanks, Yury

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