Why does numpy.power return 0 for small exponents while math.pow returns the correct answer?

    In [25]: np.power(10,-100)
    Out[25]: 0

    In [26]: math.pow(10,-100)
    Out[26]: 1e-100

I would expect both the commands to return 1e-100. This is not a precision issue either, since the issue persists even after increasing precision to 500. Is there some setting which I can change to get the correct answer?

Oh, it's much "worse" than that:

    In [2]: numpy.power(10,-1)   
    Out[2]: 0

But this is a hint to what's going on: 10 is an integer, and numpy.power doesn't coerce the numbers to floats. But this works:

    In [3]: numpy.power(10.,-1)
    Out[3]: 0.10000000000000001

    In [4]: numpy.power(10.,-100)
    Out[4]: 1e-100

Note, however, that the power operator, **, does convert to float:

    In [5]: 10**-1
    Out[5]: 0.1

From: stackoverflow.com/q/22956139

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