Question

standard power operation (**) in Python does not work for negative power! Sure I could write the formula otherwise, with divide and positive power. However, I am checking optimization routine result, and sometimes power is negative, sometimes it is positive. Here again a if statement could do, but I am wondering if there is a workarouns and a Python library where negative exposant is allowed.
Thanks and Regards.

Answer 1

Which version of python are you using? Perfectly works for me in Python 2.6, 2.7 and 3.2:

>>> 3**-3 == 1.0/3**3
True

and with numpy 1.6.1:

>>> import numpy as np
>>> arr = np.array([1,2,3,4,5], dtype='float32')
>>> arr**-3 == 1/arr**3
array([ True,  True,  True,  True,  True], dtype=bool)