[Python-ideas] Fwd: Extremely weird itertools.permutations

[David Mertz]

What would you like this hypothetical function to output here:

>>> from itertools import permutations
>>> from decimal import Decimal as D
>>> from fractions import Fraction as F
>>> items = (3, 3.0, D(3), F(3,1), "aa", "AA".lower(), "a"+"a")
>>> list(permutations(items))

It's neither QUITE equality nor identity you are looking for, I think, in
nonredundant_permutation():

>> "aa" == "AA".lower(), "aa" is "AA".lower()
(True, False)
>>> "aa" == "a"+"a", "aa" is "a"+"a"
(True, True)
>>> D(3) == 3.0, D(3) is 3.0
(True, False)

On Fri, Oct 11, 2013 at 11:38 AM, Neil Girdhar <mistersheik at gmail.com>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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-- 
Keeping medicines from the bloodstreams of the sick; food
from the bellies of the hungry; books from the hands of the
uneducated; technology from the underdeveloped; and putting
advocates of freedom in prisons.  Intellectual property is
to the 21st century what the slave trade was to the 16th.
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