Simple algorithm question - how to reorder a sequence economically

[Chris Angelico]

On Fri, May 24, 2013 at 6:47 PM, Fábio Santos <fabiosantosart at gmail.com> wrote:
>
> On 24 May 2013 09:41, "Chris Angelico" <rosuav at gmail.com> wrote:
>>
>> On Fri, May 24, 2013 at 6:14 PM, Peter Brooks
>> <peter.h.m.brooks at gmail.com> wrote:
>> > What is the easiest way to reorder a sequence pseudo-randomly?
>> >
>> > That is, for a sequence 1,2,3,4 to produce an arbitrary ordering (eg
>> > 2,1,4,3) that is different each time.
>> >
> ...
>
>> It works, it produces a unique list for any given index provided, but
>> it's not the cleanest or most efficient. But I know someone'll improve
>> on it... or tell me I'm an idiot for not taking a more obvious
>> approach :)
>>
>> ChrisA
>
> I think that is pretty much itertools.permutations from the standard
> library. The OP should check it out.

That works if all the permutations are wanted at once. Is there a way,
short of iterating over it N times, to request permutation #N? Or
maybe I'm misreading the OP and that's not a requirement.

ChrisA