title: Python: Add a column to numpy 2d array
body: <p>I have a 60000 by 200 numpy array. I want to make it 60000 by 201 by adding a column of 1's to the right. (so every row is [prev, 1])
  Concatenate with axis = 1 doesn't work because it seems like concatenate requires all input arrays to have the same dimension.
  How should I do this? I can't find any existing useful answer, and most of the answers about this were written a few years ago so things might be different now. </p>