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

Guido van Rossum guido at python.org
Tue Sep 25 20:06:04 CEST 2007

On 9/25/07, Mark Summerfield <mark at qtrac.eu> wrote:

My proposal was for the sorteddict to be put in the collections module, not as a builtin. One of the things I particularly like about Python is that the core language is small.

However, I think that the collections module is rather thin, and as you say, it is "obscure" so won't get in the way of inexperienced or casual users if it is beefed up a bit, yet could be really useful to more demanding users. On comp.lang.python, a respondent called Paul Hankin suggested a somewhat different approach to mine: he proposed a sorteddict with the same API as a dict but with a constructor that is similar to the sorted() function: sorteddict((mapping | sequence | nothing), cmp=None, key=None, reverse=None) He points out that this has a problem with keyword argument dictionaries, but that one solution is sorteddict(dict(**kwargs), ...).

Why would this be a problem? There is no requirement that sorteddict() support this feature.

From comments other people have made on this list and on comp.lang.python, it may be that Paul Hankin's approach is more popular and better than the one I proposed---the only downside being that he didn't give any hints as to an implementation.

I am hoping that Python 2.6 (and 3.0) will have a sorted dictionary of some kind, and I get the impression that it would be welcomed (in the standard library).

For that to happen, someone has to write a production-quality implementation, release it as a separate 3rd party module for a while, show that it is sufficiently stable and popular to be incorporated in the standard library, and commit to maintaining it for a few years at least. (It doesn't have to be all the same someone.)

Hoping and wishing doesn't cause working code to spring into existence.

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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