[Python-3000] ordered dict for p3k collections? (original) (raw)

Mark Summerfield mark at qtrac.eu
Fri Sep 14 21:52:23 CEST 2007

On 2007-09-14, Adam Olsen wrote:

On 9/14/07, Mark Summerfield <mark at qtrac.eu> wrote: > On 2007-09-14, Nicko van Someren wrote: > > On 11 Sep 2007, at 15:06, Mark Summerfield wrote: > > > Is there any chance that an ordered dict will be added to Python 3's > > > library? > > > > It would make sense, since one of the primary justifications for the > > new metaclass system (PEP 3115) is to allow the metaclass to provide > > order-preserving dictionaries to record the order in which members > > are defined. > > > > > I think other people must find such things useful. There are three > > > implementations on the Python Cookbook site, and one on PyPI, all in > > > pure Python (plus I have my own implementation, also pure Python). > > > > Is there much commonality between the interfaces for these? I'm sure > > there are various different opinions as to the exact nature of the > > API, particularly around any facilities for re-ordering, slicing etc. > > Cheers, > > Nicko > > After posting I realised that actually this isn't P3K-specific. I'd hope > to see the collections module extended with more data structures in > general. > > I put a similar post on the main python list but with no consensus so > far... > > I put forward an API which is the same as dict (but any list or iterator > returned "just happens" to work in key order) plus a few extra methods > to exploit the ordering. I don't know how to refer to a usenet thread > but this should get there:

That's a sorted dict. PEP 3115 wants an insertion-ordered dict. You're not the first to confuse them. ;)

Hmmm, I'd not come across that terminology distinction before. I guess I'll have to rename mine then.

BTW In my previous I said "I hope for example, that an AVL tree and/or a B*tree and/or a skiplist will be implemented." Actually, I don't care what data structures are used, I just think that Python lacks ordered data structures, specifically: sorteddict and sortedset. (Personally I've never needed an insertion-ordered dict.)

-- Mark Summerfield, Qtrac Ltd., www.qtrac.eu

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