Interesting. It's more than a couple of lines of code to change for Jython (I tried), but now that we require Java 7, we should be able to implement identical ordered behavior to PyPy for dict, __dict__, set, and frozenset using ConcurrentSkipListMap instead of our current usage of ConcurrentHashMap. (Other collections like defaultdict and weakref collections use Google Guava's MapMaker, which doesn't have an ordered option.)

I think this is a great idea from a user experience perspective.

On Thu, Feb 5, 2015 at 3:04 PM, Amaury Forgeot d'Arc <> wrote:
2015-02-05 23:02 GMT+01:00 Chris Barker <>:
Interesting -- somehow this message came through on the google group mirror of  python-ideas only -- so replying to it barfed.

He's my reply again, with the proper address this time:

On Wed, Feb 4, 2015 at 1:14 PM, Neil Girdhar <> wrote:
Hundreds of people want an orderedset ( and yet the ordered sets that are in PyPI (oset, ordered-set) are incomplete.  Please consider adding an ordered set that has *all* of the same functionality as set.
(If anyone wants to add a complete ordered set to PyPI that would also be very useful for me!)

It seems like a good way to go here is to contribute to one of the projects already on PyPI -- and once you like it, propose that it be added to the standard library.

And can you leverage the OrderedDict implementation already in the std lib? Or maybe better, the new one in PyPy?

PyPy dicts and sets (the built-in ones) are already ordered by default. 

Amaury Forgeot d'Arc

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