[RickMuller]
> I have to sort a list, but in addition to the sorting, I need to
> compute a phase factor that is +1 if there is an even number of
> interchanges in the sort, and -1 if there is an odd number of
> interchanges.
This sounds like a homework problem but will offer a solution anyway:
>>> phase = 1
>>> def mycmp(x, y):
global phase
phase = -phase
return cmp(x, y)
>>> sorted('abracadabra', cmp=mycmp)
['a', 'a', 'a', 'a', 'a', 'b', 'b', 'c', 'd', 'r', 'r']
>>> phase
-1
Raymond Hettinger
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