On Wed, Dec 12, 2012 at 3:37 PM, Dag Sverre Seljebotn <d.s.seljeb...@astro.uio.no> wrote: > On 12/12/2012 01:15 AM, Nick Coghlan wrote: >> >> On Wed, Dec 12, 2012 at 5:37 AM, Dino Viehland <di...@microsoft.com >> <mailto:di...@microsoft.com>> wrote: >> >> OTOH changing certain dictionaries in IronPython (such as keyword >> args) to be >> ordered would certainly be possible. Personally I just wouldn't >> want to see it >> be the default as that seems like unnecessary overhead when the >> specialized >> class exists. >> >> >> Which reminds me, I was going to note that one of the main gains with >> ordered keyword arguments, is their use in the construction of >> string-keyed objects where you want to be able to control the order of >> iteration (e.g. for serialisation or display purposes). Currently you >> have to go the path of something like namedtuple where you define the >> order of iteration in one operation, and set the values in another. > > > So here's a brand new argument against ordered dicts: The existence of > perfect hashing schemes. They fundamentally conflict with ordered dicts.
If I understand your explanation, then they don't conflict with the type of ordering described in this thread. Raymond's optimization separates the "hash table" part from the "contents" part of a dictionary, and there is no requirement that these two parts be in the same size or the same order. Indeed, Raymond's split design lets you re-parameterize the hashing all you want, without perturbing the iteration order at all. You would in fact be able to take a dictionary at any moment, and say, "optimize the 'hash table' part to a non-colliding state based on the current contents", without touching the 'contents' part at all. (One could do this at class creation time on a class dictionary, and just after importing on a module dictionary, for example.) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
