[Python-Dev] Change to yield-from implementation

Guido van Rossum guido at python.org
Mon Apr 9 16:57:05 CEST 2012

On Mon, Apr 9, 2012 at 5:46 AM, Antoine Pitrou <solipsis at pitrou.net> wrote:
> On Tue, 10 Apr 2012 00:24:07 +1200
> Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
>> Mark Shannon wrote:
>> > We have recently removed the f_yieldfrom field from the frame object.
>> > (http://bugs.python.org/issue14230)
>> Hey, wait a minute. Did anyone consider the performance effect
>> of that change on deeply nested yield-froms?
> What's the point? Apart from naïve toy examples of traversing trees, I
> don't think "deeply nested yield-froms" are likely to be
> performance-critical.

I agree with Benjamin that correctness trumps performance, but I'd
also like to point out that there are other use cases besides nested
iterators. If this gets used for coroutines it may not be so unusual
to have a stack of nested things with on top one that loops a lot --
if each iteration incurs cost proportional to how it got there this
may be a problem. But, correctness first.

--Guido van Rossum (python.org/~guido)

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