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[Python-ideas] Revised**5 PEP on yield-from

Ron Adam rrr at ronadam.com
Thu Mar 5 19:31:38 CET 2009 
Greg Ewing wrote:

> This is only a speed issue if the time taken to find the
> "top" starting from one of the "bottoms" is a significant
> component of the total running time. My conjecture is that
> it won't be, especially if you do it iteratively in a
> tight C loop.


Could it be possible to design it so that the yield path of generators are 
passed down or forwarded to sub-generators when they are called?  If that 
can be done then no matter how deep they get, it works as if it is always 
only one generator deep.

So...

      result = yield from sub-generator

Might be sugar for ...  (very rough example)

      sub-generator.forward(this_generator_yield_path)  # set yield path
      sub_generator.run()         # pass control to sub-generator
      result = sub_generator.return_value     # get return value if set

Of course the plumbing in this may takes some creative rewriting of 
generators so the yield path can be passed around.  Being able to get the 
yield path might also be useful in other ways, such as error reporting.

Cheers, Ron
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