Dangerous behavior of list(generator)

[Carl Banks]

On Dec 14, 2:48 pm, Steven D'Aprano <st... at REMOVE-THIS-
cybersource.com.au> wrote:
> On Mon, 14 Dec 2009 14:31:44 +0000, exarkun wrote:
> > On 06:46 am, tjre... at udel.edu wrote:
> >>On 12/13/2009 10:29 PM, exar... at twistedmatrix.com wrote:
> >>>Doesn't matter. Sometimes it makes sense to call it directly.
>
> >>It only makes sense to call next (or .__next__) when you are prepared to
> >>explicitly catch StopIteration within a try..except construct. You did
> >>not catch it, so it stopped execution.
>
> >>Let me repeat: StopIteration is intended only for stopping iteration.
> >>Outside that use, it is a normal exception with no special meaning.
>
> > You cut out the part of my message where I wrote that one might have
> > forgotten the exception handling code that you posit is required, and
> > that the current behavior makes debugging this situation unnecessarily
> > challenging.
>
> I don't see why you think this is any more challenging to debug than any
> other equivalent bug.

"Errors should never pass silently."

I'm not saying it's necessarily difficult to debug--although building
a list by hand to test it is a lot more work than reading an exception
traceback--but it'a stark violation of a Zen and common sense, so it
is more serious than other sorts of errors.


Carl Banks