>>> l = [1.0, 2.0, 3.0, float('nan'), 4.0, 3.0, 2.0, 1.0]
>>> l.sort()
>>> l
[1.0, 2.0, 3.0, nan, 1.0, 2.0, 3.0, 4.0]

The expected result is either of the following:
[nan, 1.0, 1.0, 2.0, 2.0, 3.0, 3.0, 4.0] (similar to None)
[1.0, 1.0, 2.0, 2.0, 3.0, 3.0, 4.0, nan] (similar to string 'nan')