[Python-ideas] Revised^4 PEP on yield-from

Antoine Pitrou solipsis at pitrou.net
Fri Feb 20 01:39:56 CET 2009

Greg Ewing <greg.ewing at ...> writes:
> Traversing it with a generator:
>    def traverse(node):
>      if node:
>        yield process_node(node)
>        yield from traverse(node.left)
>        yield from traverse(node.right)
> Do you still think an unrolled version would be
> equally clear? If so, you have extremely different
> tastes from me!

Of course, I admit the "yield from" version is simpler :) However, if there
isn't a specialized optimization in the interpreter, it will also probably be
slower (because it switches between frames a lot, which is likely expensive,
although I don't know of any timings).
Besides, my point was to show that you didn't /need/ "yield from" to write a
linear traversal generator, and the 15 or so lines of that generator are
sufficiently generic to be reused from project to project.

(my opinion on your PEP being that it brings the complication inside the
interpreter itself, especially if you want to implement the feature in an
optimized way. I haven't read the scheduler example yet, though...)



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