Problem with OrderedDict - progress report

[Chris Angelico]

On Sat, Jun 2, 2018 at 9:10 AM, Gregory Ewing
<greg.ewing at canterbury.ac.nz> wrote:
> Chris Angelico wrote:
>>
>> if you 'break' immediately after a mutation, that isn't
>> continuing to iterate. Even though you're inside the loop, there's no
>> further action taken to process the loop, and no problem.
>
>
> Yes, but you're also not calling next() again, so no
> exception would be triggered.
>
> My point is that I don't see a justification for treating
> the last next() call (the one that notices you've reached
> the end and raises StopIteration) any differently from
> the others. It seems like either a bug or a misfeature
> to me.
>

I'm guessing it's pure chance, and that certain types of mutation
would still trigger the exception.

A bit of background: These exceptions exist to prevent interpreter
crashes. I believe originally you'd only get an exception if the
mutation triggered a dictionary resize; in other words, if NOT giving
an exception would have actually segfaulted the interpreter right then
and there. (I'm talking CPython here, obviously. No idea what other
Pythons did at the time.) It's more consistent now; but it looks like
you may have come across a residual inconsistency. ISTM it would
indeed be more logical to raise for this situation too.

ChrisA