[Python-ideas] The async API of the future: yield-from

Calvin Spealman ironfroggy at gmail.com
Tue Oct 16 17:18:22 CEST 2012

On Mon, Oct 15, 2012 at 8:55 PM, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
> Calvin Spealman wrote:
>> I'm still -1 on delegating control to subgenerators with yield-from,
>> versus having the scheduler just deal with them directly.
> Do you mean to *disallow* using yield-from for this, or just
> not to encourage it?
> I don't see how you *could* disallow it; there's no way for
> the scheduler to know whether one of the generators it's
> handling is delegating using yield-from.
> I also can't see any reason you would want to discourage it.
> Given that yield-from exists, it's an obvious thing to do.

I have since changed my position slightly. I don't want to disallow it, no.
I don't want to discourage, no. But, I do think *both* are useful.

I think "yield from" is the obvious way to "call" between tasks, but that
there are other cases when we want to spawn a task to begin without
blocking our task, and that "yield" should be used here. We should be
table to simply yield a task to tell the scheduler to start it,
possibly getting a Future in return which we can use to get the
eventual result. This may make it easier to do multiple sub-tasks
together. We might yield N tasks, and then "yield from wait(futures)"
to wait for them all to complete.

> --
> Greg
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