Re: [Python-Dev] PEP 431 Updates

On 28/01/13 23:52, Antoine Pitrou wrote:

Le Mon, 28 Jan 2013 22:31:29 +1000, Nick Coghlan a écrit :

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6. Under "New collections"

Why both lists and sets?

Because pytz did it. But yes, you are right, an ordered set is a better solution. Baseing it on OrderedDict seems like a hack, though. I could implement a custom orderedset, of course.

Sets themselves have an honourable history of just being a thin wrapper around dictionaries with all the values set to None (although they're not implemented that way any more). Whether you create an actual OrderedSet class, or just expose the result of calling keys() on an OrderedDict instance is just an implementation detail, though.

Why the complication? Just expose a regular set and let users call sorted() if that's what they want.

An OrderedSet is not a sorted set. An OrderedSet, like an OrderedDict, remembers *insertion order*, it does not automatically sort the keys. So if datetime needs an ordered set, and I have no opinion on whether or not it really does, calling sorted() on a regular set is not the solution. -- Steven