[Python-ideas] Extremely weird itertools.permutations

[Neil Girdhar]

Note that if permutations is made to return only unique permutations, the 
behaviour of defining unique elements by index can be recovered using:

([it[index] for index in indexes] for indexes in 
itertools.permutations(range(len(it))))

On Friday, October 11, 2013 2:38:33 PM UTC-4, Neil Girdhar wrote:
>
> "It is universally agreed that a list of n distinct symbols has n! 
> permutations. However, when the symbols are not distinct, the most common 
> convention, in mathematics and elsewhere, seems to be to count only 
> distinct permutations." — 
> http://stackoverflow.com/questions/6534430/why-does-pythons-itertools-permutations-contain-duplicates-when-the-original
> .
>
>
> Should we consider fixing itertools.permutations and to output only unique 
> permutations (if possible, although I realize that would break code). It is 
> completely non-obvious to have permutations returning duplicates. For a 
> non-breaking compromise what about adding a flag?
>
> Best,
> Neil
>
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