[Python-Dev] async/await behavior on multiple calls

[Guido van Rossum]

Agreed. (But let's hear from the OP first.)

On Tue, Dec 15, 2015 at 12:27 PM, Andrew Svetlov <andrew.svetlov at gmail.com>
wrote:

> Both Yury's suggestions sounds reasonable.
>
> On Tue, Dec 15, 2015 at 10:24 PM, Yury Selivanov
> <yselivanov.ml at gmail.com> wrote:
> > Hi Roy and Guido,
> >
> > On 2015-12-15 3:08 PM, Guido van Rossum wrote:
> > [..]
> >>
> >>
> >> I don't know how long you have been using async/await, but I wonder if
> >> it's possible that you just haven't gotten used to the typical usage
> >> patterns? In particular, your claim "anything that takes an `awaitable`
> has
> >> to know that it wasn't already awaited" makes me sound that you're just
> >> using it in an atypical way (perhaps because your model is based on
> other
> >> languages). In typical asyncio code, one does not usually take an
> awaitable,
> >> wait for it, and then return it -- one either awaits it and then
> extracts
> >> the result, or one returns it without awaiting it.
> >
> >
> > I agree.  Holding a return value just so that coroutine can return it
> again
> > seems wrong to me.
> >
> > However, since coroutines are now a separate type (although they share a
> lot
> > of code with generators internally), maybe we can change them to throw an
> > error when they are awaited on more than one time?
> >
> > That should be better than letting them return `None`:
> >
> >     coro = coroutine()
> >     await coro
> >     await coro  # <- will raise RuntimeError
> >
> >
> > I'd also add a check that the coroutine isn't being awaited by more than
> one
> > coroutine simultaneously (another, completely different issue, more on
> which
> > here: https://github.com/python/asyncio/issues/288).  This was fixed in
> > asyncio in debug mode, but ideally, we should fix this in the interpreter
> > core.
> >
> > Yury
> > _______________________________________________
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> >
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>
>
>
> --
> Thanks,
> Andrew Svetlov
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-- 
--Guido van Rossum (python.org/~guido)
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