Divide one numpy array by another only where both arrays are non-zero

Question

What\'s the easiest, most Pythonic way to divide one numpy array by another (of the same shape, element-wise) only where both arrays are non-zero?

Where either the d

Answer 1

I would do it in two lines:

z = x/y
z[y == 0] = 0

As you said, if only the element in x is 0, z will already be 0 at that position. So let NumPy handle that, and then fix up the places where y is 0 by using NumPy's boolean indexing.

Answer 2

This still tries to divide by 0, but it gives the correct result:

np.where(b==0, 0, a/b)

To avoid doing the divide-by-zero, you can do:

m = b!=0
c = np.zeros_like(a)
np.place(c, m, a[m]/b[m])