Original question
I am getting a very odd error message when I try to assign some of the elements of an array. I am using a combination of a slice and a set of indices. See the following simple example.
import scipy as sp
a = sp.zeros((3, 4, 5))
b = sp.ones((4, 5))
I = sp.array([0, 1, 3])
b[:, I] = a[0, :, I]
This code raises the following ValueError:
ValueError: shape mismatch: value array of shape (3,4) could not be broadcast to indexing result of shape (3,4)
--
Follow up
Be careful when using a combination of a slice and seq. of integers. As pointed out on github:
x = rand(3, 5, 7)
print(x[0, :, [0,1]].shape)
# (2, 5)
print(x[0][:, [0,1]].shape)
# (5, 2)
This is how numpy is designed to work, but it is nevertheless a bit confusing that x[0][:, I] is not the same as x[0, :, I]. Since this is the behavior I want I choose to use x[0][:, I] in my code.