Looking over the code base, frozensets are used rarely. So I don't
think this is warranted.
On Jan 24, 2008 2:32 PM, Raymond Hettinger <[EMAIL PROTECTED]> wrote:
> I think it would be more useful for the {e1, e2, e3} literal to be a
> frozenset instead of a set.
>
> In expressions like "x in {'html', 'xml', 'php'}" the compiler could optimize
> away the set construction and treat it as a constant.
>
> In cases where we want to build-up mutable sets, we need to start with set()
> anyway:
>
> s = set()
> for elem in source:
> s.add(elem)
>
> I don't think it would be typical to start with a partially filled-out set
> and then build-t up further:
>
> s = {'a', 'b', 'c'} # rare use-case
> for elem in source:
> s.add(elem)
>
> One of the primary use cases for frozensets is to be members of other sets or
> to be keys in a dict (esp. for graph representations). The repr's of those
> nested structures are annoying to read because the word "frozenset" gets
> spelled-out over and over again. Here's a few lines from the pprint() output
> for a graph of a cube:
>
> {frozenset([0, 1]): frozenset([frozenset([0]),
> frozenset([1]),
> frozenset([0, 1, 2])]),
> frozenset([0, 1, 2]): frozenset([frozenset([1, 2]),
> frozenset([0, 2]),
> frozenset([0, 1])])}
>
>
> This would read *much* better with the new notation:
>
> {{0, 1}: {{0},
> {1},
> {0, 1, 2}},
> {0, 1, 2}: {{1, 2},
> {0, 2},
> {0, 1}}}
>
> If you want to see how extremely bad the current repr's can get, see the repr
> for David Eppstein's cuboctahedron in the tests for pprint:
> http://mail.python.org/pipermail/python-checkins/2008-January/065099.html
>
> In short, I think we would be much better served by using the {} literal
> notation for frozensets.
>
> Raymond
>
>
> P.S. A small side-benefit is it may put an end for interminable requests for
> a {:} or {/} notation for empty sets. There's not much need for a literal
> for a empty frozenset (use "not s" instead).
>
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--
--Guido van Rossum (home page: http://www.python.org/~guido/)
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