On Tue, Nov 7, 2017, at 09:56, Steven D'Aprano wrote: > Don't let the perfect be the enemy of the good. > > For many applications, keys are never removed from the dict, so this > doesn't matter. If you never delete a key, then the remaining keys will > never be reordered. > > I think that Nick's intent was not to say that after a single deletion, > the ordering guarantee goes away "forever", but that a deletion may be > permitted to reorder the keys, after which further additions will honour > insertion order. At least, that's how I interpret him.
Honestly, I think the more intuitive way would be the "other way around" - deletions don't themselves change the order, but they do cause subsequent insertions to be allowed to insert at places other than the end. Does the implementation in CPython have this property? One way I have seen this done is that the items themselves live in an array, and each new item is always inserted in the first empty slot in the array (empty slots form a freelist). The hash buckets contain indices into the array. _______________________________________________ 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
