Perform numpy exp function in-place

Question

As in title, I need to perform numpy.exp on a very large ndarray, let's say ar, and store the result in ar itself. Can this operation be performed in-place?

Answer 1

You can use the optional outargument of exp:

a = np.array([3.4, 5])
res = np.exp(a, a)
print(res is a)
print(a)

Output:

True
[  29.96410005  148.4131591 ]

exp(x[, out])

Calculate the exponential of all elements in the input array.

Returns

out : ndarray Output array, element-wise exponential of x.

Here all elements of a will be replaced by the result of exp. The return value res is the same as a. No new array is created