Python: sort function breaks in the presence of nan

Question

sorted([2, float(\'nan\'), 1]) returns [2, nan, 1]

(At least on Activestate Python 3.1 implementation.)

I understand nan

Answer 1

I'm not sure about the bug, but the workaround may be the following:

sorted(
    (2, 1, float('nan')),
    lambda x,y: x is float('nan') and -1 
                or (y is float('nan') and 1
                or cmp(x,y)))

which results in:

('nan', 1, 2)

Or remove nans before sorting or anything else.