2016-04-15 23:16 GMT+02:00 Ethan Furman <et...@stoneleaf.us>: >> It's an useful property. For example, let's say that you have a guard >> on globals()['value']. The guard is created with value=3. An unit test >> replaces the value with 50, but then restore the value to its previous >> value (3). Later, the guard is checked to decide if an optimization >> can be used. > > I don't understand -- shouldn't the version be incremented with the value > was replaced with 50, and again when re-replaced with 3?
Oh wait, I'm tired and you are right. Not increasing the value only helps on this code: dict[key] = value dict[key] = value # version doesn't change >> If the dictionary values are modified during the loop, the dict >> version is increased. But it's allowed to modify values when you >> iterate on *keys*. > > I don't understand. Could you provide a small example? For example, this loop is fine: for key in dict: dict[key] = None In this loop, the dict version is increased at each loop iteration. For iter(dict), the check prevents a crash. The following example raises a RuntimeError("dictionary changed size during iteration"): d={1:2} for k in d: d[k+1] = None Victor _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com