On Tue, May 14, 2013 at 9:07 PM, Ethan Furman <ethan@stoneleaf.us> wrote:
On 05/14/2013 06:57 PM, Don Spaulding wrote:
On Tue, May 14, 2013 at 5:23 PM, Andrew Barnert <abarnert@yahoo.com <mailto:abarnert@yahoo.com>> wrote:

    On May 14, 2013, at 12:53, Jonathan Eunice <jonathan.eunice@gmail.com <mailto:jonathan.eunice@gmail.com>> wrote:

    Using a compatible, separate implementation for |OrderedDict| is a fine way to gracefully extend the language, but
    it leaves ordering only half-accomodated. Consider:

    OrderedDict(a=2,  b=3,  c=7)

    If your proposal is to replace dict with OrderedDict, I think you need at least one use case besides OrderedDict's

I don't understand the dismissal of OrderedDict.__init__ as an invalid use case.

It's not being dismissed, but it's only one.  There are thousands of functions using **kwds that simply don't care about the order.  Should they all pay the performance price so that some tiny fraction can benefit?

While it is correctly said that if performance is a Big Deal you shouldn't be using Python, we also are not interested in making it slower without a really good reason.

I'm of the opinion that the status quo is "fast, but kinda wrong".  Ideally we'd have a "fast, and correct" implementation, but I'd settle for a "negligibly slower, but still correct" implementation.  Nobody wants Python 3-dot-next to be slower, but how much slower are we really talking about given that Raymond Hettinger recently proposed[0] a plain-old-dict implementation that uses less space, performs better, and as an unintended side-effect just happens to maintain its initial order?

Aside from the performance impact, isn't any code that relies on any current ordering behavior of **kwargs broken by design?

[0]: http://mail.python.org/pipermail/python-dev/2012-December/123028.html