>>> import numpy
>>> print numpy.power.__doc__
power(x1, x2[, out])
First array elements raised to powers from second array, element-wise.
Raise each base in `x1` to the positionally-corresponding power in
`x2`. `x1` and `x2` must be broadcastable to the same shape.
Parameters
----------
x1 : array_like
The bases.
x2 : array_like
The exponents.
Returns
-------
y : ndarray
The bases in `x1` raised to the exponents in `x2`.
Examples
--------
Cube each element in a list.
>>> x1 = range(6)
>>> x1
[0, 1, 2, 3, 4, 5]
>>> np.power(x1, 3)
array([ 0, 1, 8, 27, 64, 125])
Raise the bases to different exponents.
>>> x2 = [1.0, 2.0, 3.0, 3.0, 2.0, 1.0]
>>> np.power(x1, x2)
array([ 0., 1., 8., 27., 16., 5.])
The effect of broadcasting.
>>> x2 = np.array([[1, 2, 3, 3, 2, 1], [1, 2, 3, 3, 2, 1]])
>>> x2
array([[1, 2, 3, 3, 2, 1],
[1, 2, 3, 3, 2, 1]])
>>> np.power(x1, x2)
array([[ 0, 1, 8, 27, 16, 5],
[ 0, 1, 8, 27, 16, 5]])
>>>
As per the discussed observation on numerical precision as per @GarethRees objection in comments:
>>> a = numpy.ones( (3,3), dtype = numpy.float96 ) # yields exact output
>>> a[0,0] = 0.46002700024131926
>>> a
array([[ 0.460027, 1.0, 1.0],
[ 1.0, 1.0, 1.0],
[ 1.0, 1.0, 1.0]], dtype=float96)
>>> b = numpy.power( a, 2 )
>>> b
array([[ 0.21162484, 1.0, 1.0],
[ 1.0, 1.0, 1.0],
[ 1.0, 1.0, 1.0]], dtype=float96)
>>> a.dtype
dtype('float96')
>>> a[0,0]
0.46002700024131926
>>> b[0,0]
0.21162484095102677
>>> print b[0,0]
0.211624840951
>>> print a[0,0]
0.460027000241
>>> c = numpy.random.random( ( 1000, 1000 ) ).astype( numpy.float96 )
>>> import zmq
>>> aClk = zmq.Stopwatch()
>>> aClk.start(), c**2, aClk.stop()
(None, array([[ ...]], dtype=float96), 5663L) # 5 663 [usec]
>>> aClk.start(), c*c, aClk.stop()
(None, array([[ ...]], dtype=float96), 6395L) # 6 395 [usec]
>>> aClk.start(), c[:,:]*c[:,:], aClk.stop()
(None, array([[ ...]], dtype=float96), 6930L) # 6 930 [usec]
>>> aClk.start(), c[:,:]**2, aClk.stop()
(None, array([[ ...]], dtype=float96), 6285L) # 6 285 [usec]
>>> aClk.start(), numpy.power( c, 2 ), aClk.stop()
(None, array([[ ... ]], dtype=float96), 384515L) # 384 515 [usec]