My intuition is that we want Python to be "complete".  Many other languages can find the permutations of a multiset.  Python has a permutations function.  Many people on stackoverflow expected that function to be able to find those permutations.

One suggestion: Why not make it so that itertools.permutations checks if its argument is an instance of collections.Mapping?  If it is, we could interpret the items as a mapping from elements to positive integers, which is a compact representation of a multiset.  Then, it could do the right thing for that case.

Best,
Neil




On Sat, Oct 12, 2013 at 11:03 PM, Raymond Hettinger <raymond.hettinger@gmail.com> wrote:

On Oct 12, 2013, at 6:47 PM, Steven D'Aprano <steve@pearwood.info> wrote:

the proposal is not to eliminate duplicates from 
the population, but from the permutations themselves.

I'm curious about the use cases for this.
Other than red/blue marble examples and some puzzle problems,
does this come-up in any real problems?  Do we actually need this?


Raymond

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