How can I add a column to a numpy array

Question

How can I add a column containing only "1" to the beginning of a second numpy array.

X = np.array([1, 2], [3, 4], [5, 6])

I want to have X become

[[1,1,2], [1,3,4],[1,5,6]]

Answer 1

• You can use the np.insert

  new_x = np.insert(x, 0, 1, axis=1)
  

• You can use the np.append method to add your array at the right of a column of 1 values

  x = np.array([[1, 2], [3, 4], [5, 6]])
  ones = np.array([[1]] * len(x))
  new_x = np.append(ones, x, axis=1)
  

Both will give you the expected result

[[1 1 2]
 [1 3 4]
 [1 5 6]]

Answer 2

Try this:

>>> X = np.array([[1, 2], [3, 4], [5, 6]])
>>> X
array([[1, 2],
       [3, 4],
       [5, 6]])

>>> np.insert(X, 0, 1, axis=1)
array([[1, 1, 2],
       [1, 3, 4],
       [1, 5, 6]])