[Python-Dev] Using async/await in place of yield expression

Antoine Pitrou solipsis at pitrou.net
Mon Nov 27 04:12:54 EST 2017

On Mon, 27 Nov 2017 00:41:55 -0800
Nathaniel Smith <njs at pobox.com> wrote:
> Since most libraries assume that they control both __await__ and the
> coroutine runner, they don't tend to give great error messages here
> (though trio does [2] ;-)). I think this is also why the asyncio docs
> don't talk about this. I guess in asyncio's case it is technically a
> semi-public API because you need to know how it works if you're the
> author of a library like tornado or twisted that wants to integrate
> with asyncio. But most people aren't the authors of tornado or
> twisted, and the ones who are already know how this works, so the lack
> of docs isn't a huge deal in practice...

This does seem to mean that it can be difficult to provide a __await__
method that works with different coroutine runners, though.  For
example, Tornado Futures implement __await__ for compatibility with the
asyncio event loop.  But what if Tornado wants to make its Future class
compatible with an event loop that requires a different __await__



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