[Python-3000] Iterators for dict keys, values, and items == annoying :)

[Nick Coghlan]

Adam DePrince wrote:
> There seemed to be a concensus in the community on the size of the view
> proposal, and I'm reimplementing the PEP to reflect that.  But what I
> can't resolve is the other anciliary issue: "To list or iter."  I'm not
> yet ready to resolve that issue.  The views don't resolve it either, and
> by their nature are biased towards the iter approach.  They provide
> __iter__ because its light weight to do, but there is no way a light
> weight view can provide you with ordering information from an unordered
> datastore.  Now, as a means of resolving this conflict, I'm open to the
> notion of a view implementing both __iter__ and an explicit .list method
> to avoid any extra overhead in generating a list from an iter instead of
> directly from the dict as we do now.

Umm, the whole point of the views discussion is the realisation that "list or 
iterator" is a false dichotomy. The correct answer is "new iterable that looks 
like a container in its own right, but is really just a view of the original".

As far as the value-based comparison goes, yes, in reality the view will need 
to have greater knowledge of the underlying container than in my sample 
classes in order to be sure of getting a consistent ordering from the 
underlying objects.

As Python's own set and dict show, however, unordered collections can be 
legitimately compared by value.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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