Le 06/11/2013 06:41, Nick Coghlan a écrit :
The behaviour of mutating builtin containers while iterating over them
is formally undefined beyond "it won't segfault" (one of the few such
undefined behaviours in Python). The associated exceptions are thus
strictly "best effort given other constraints".
Not sure what you mean with "formally undefined". For example, you can
perfectly well change a list's contents while iterating over it, and I
bet there's a lot of code that relies on that, as in::
for i, value in enumerate(mylist):
if some_condition(value):
mylist[i] = some_function(value)
If you change "builtin containers" to "builtin unordered containers",
then you probably are closer to the truth :)
>or perhaps some performance measurements that would show there is no
performance based reason to not have the patch added. (I can try to do
the performance part myself if necessary, I'm just not sure what all the
steps are yet.)
If the benchmark suite indicates there's no measurable speed penalty
then such a patch may be worth reconsidering. I'd be astonished if that
was actually the case, though - the lowest impact approach I can think
of is to check for live iterators when setting a dict entry, and that
still has non-trivial size and speed implications.
I think Serhiy's patch is much simpler than that (is it Serhiy's? I
think so).
Regards
Antoine.
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