[Python-ideas] Extremely weird itertools.permutations

[Neil Girdhar]

+1


On Sat, Oct 12, 2013 at 4:18 AM, TB <bauertomer at gmail.com> wrote:

> On 10/12/2013 10:35 AM, Steven D'Aprano wrote:
>
>> If you want a unique_permutations generator, that's a reasonable
>> request. If you insist on changing permutations, that's unreasonable,
>> firstly because the current behaviour is correct, and secondly because
>> backwards compatibility would constrain it to keep the existing
>> behaviour even if it were wrong.
>>
>>  I agree that backwards compatibility should be kept, but the current
> behaviour of itertools.permutations is (IMHO) surprising.
>
> So here are my 2c: Until I tried it myself, I was sure that it will be
> like the corresponding permutations functions in Sage:
>
> sage: list(Permutations("aba"))
> [['a', 'a', 'b'], ['a', 'b', 'a'], ['b', 'a', 'a']]
>
> or Mathematica: http://www.wolframalpha.com/**input/?i=permutations+of+{a%
> **2C+b%2C+a}<http://www.wolframalpha.com/input/?i=permutations+of+%7Ba%2C+b%2C+a%7D>
>
> Currently the docstring of itertools.permutations just says "Return
> successive r-length permutations of elements in the iterable", without
> telling what happens with input of repeated elements. The full doc in the
> reference manual is better in that regard, but I think at least one example
> with repeated elements would be nice.
>
> Regards,
> TB
>
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