Python, Numpy: How to change two vectors at once

Question

I'm trying to change two vectors of a NumPy matrix at once, but I'm losing one vector components:

import numpy as np

data = np.array([[1, 2, 3, 4],[1, 2, 3, 4],[1, 2, 3, 4],[1, 2, 3, 4]])
last = data[:, -1]
print(last)
data[:, 1:] = data[:, :-1]
data[:, 0] = last

print(data)

Gives this result:

[4 4 4 4]
[[3 1 2 3]
 [3 1 2 3]
 [3 1 2 3]
 [3 1 2 3]]

But I want to maintain the 4s in the first column. Is there any form to accomplish that?

Answer 1

Use:

>>> np.roll(data, 1, 1)
array([[4, 1, 2, 3],
       [4, 1, 2, 3],
       [4, 1, 2, 3],
       [4, 1, 2, 3]])