[Python-3000] Is this a bug with list comprehensions or not?

Greg Ewing greg.ewing at canterbury.ac.nz
Sat Jul 12 02:11:02 CEST 2008

Stefan Behnel wrote:

> While I agree with this being bad design, I do think that the above is a bug.
> It's a different thing if the iterable in the list comp/genexp raises a
> StopIteration, or if the conditional does it. And not silently catching
> anything raised by the latter sounds like the right thing to me.

 From some experiments I just did using bare genexps and calling
next() on them, I don't think anything is being silently caught
in the genexp. What's happening is that the surrounding list()
constructor is performing another level of iteration over the
results of the genexp, and *that* is what's being stopped by
the StopIteration.

I don't see how this can be fixed, because there's no way for
the list() constructor to know where the StopIteration is coming

Or maybe I misunderstand what you think the resolution of this
should be. What behaviour do you want to see in this situation?


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