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

Mark Summerfield mark at qtrac.eu
Sat Sep 15 07:04:18 CEST 2007

On 2007-09-14, Martin v. Löwis wrote:

>> 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.

I think "insertion-ordered" is over-specification, just to make the distinction clear. Most of the time, people mean "ordered dictionary" to say "keys are in a fixed order" - typically insertion order. When they want to express that the keys ought to be sorted, they call it "sorted dictionary".

I got my terminology from C++ which has

C++ map           => Python sorteddict (missing!)
C++ unordered_map => Python dict
C++ set           => Python sortedset (missing!)
C++ unordered_set => Python set

I've now renamed mine to sorteddict: http://pypi.python.org/pypi/sorteddict

As for Adam's comment about the dict API, I find it okay, and I think some people would prefer a close match. Unfortunately, I don't think there will ever be consensus (so that's why there's a BDFL), but whatever their APIs, I hope that Python gets a sorteddict and a sortedset. But how does this happen? I've discussed it on comp.lang.python (having used ordereddict in the subject line to create unintentional confusion), but at some point a PEP has to be created. I'm happy to do that (at least for a sorteddict), but if someone who has done PEPs before did so, I'd be just as happy---I'll see what the feedback is (if any) when I get online again next week.

PS And no, I've never programmed in PHP and never fancied doing so:-)

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

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