Python: Add a column to numpy 2d array

Question

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 wor

Answer 1

Using numpy index trick to append a 1D vector to a 2D array

a = np.zeros((6,2))
# array([[ 0.,  0.],
#        [ 0.,  0.],
#        [ 0.,  0.],
#        [ 0.,  0.],
#        [ 0.,  0.],
#        [ 0.,  0.]])
b = np.ones(6) # or np.ones((6,1))
#array([1., 1., 1., 1., 1., 1.])
np.c_[a,b]
# array([[0., 0., 1.],
#        [0., 0., 1.],
#        [0., 0., 1.],
#        [0., 0., 1.],
#        [0., 0., 1.],
#        [0., 0., 1.]])