[Python-ideas] Revised**12 PEP on Yield-From

[Jacob Holm]

Hi Erik

Erik Groeneveld wrote:
> There is one problem left however.  The code dealing with
> GeneratorExit has to undo the work of close() a bit.  To account for:
> 
>       "If this call results in an exception, it is propagated to the delegating
>       generator. Otherwise, GeneratorExit is raised in the delegating
> generator."
> 
> and knowing that close() raises a RuntimeError when a generator
> ignores GeneratorExit, I have:
> 
>                     try:
>                         generator.close()
>                     except RuntimeError:
>                         pass
>                     raise GeneratorExit
> 
> But this code cannot tell if the generator intended to raise a
> RuntimeError. 

Why do you think you can't just do:

    generator.close()
    raise GeneratorExit

instead?

This does excatly what the quote says, and if you look at the expansion 
in the PEP that is exactly how it is defined there.

HTH
-Jacob