[Python-Dev] PEP 492: What is the real goal? (original) (raw)

Jim J. Jewett jimjjewett at gmail.com
Fri May 1 21:48:51 CEST 2015

On Fri, May 1, 2015 at 2:59 PM, Guido van Rossum <guido at python.org> wrote:

On Fri, May 1, 2015 at 11:26 AM, Jim J. Jewett <jimjjewett at gmail.com> wrote:

On Thu, Apr 30, 2015 at 3:32 PM, Guido van Rossum <guido at python.org> wrote:

(Guido:)> Actually that's not even wrong. When using generators as coroutines, PEP 342 > style, "yield" means "I am blocked waiting for a result that the I/O > multiplexer is eventually going to produce".

So does this mean that yield should NOT be used just to yield control if a task isn't blocked? (e.g., if its next step is likely to be long, or low priority.) Or even that it wouldn't be considered a co-routine in the python sense?

I'm not sure what you're talking about. Does "next step" refer to something in the current stack frame or something that you're calling?

The next piece of your algorithm.

None of the current uses of "yield" (the keyword) in Python are good for lowering priority of something.

If there are more tasks than executors, yield is a way to release your current executor and go to the back of the line. I'm pretty sure I saw several examples of that style back when coroutines were first discussed.

-jJ

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