How to Add Column in NumPy

This tutorial will introduce the method to add a column to a NumPy array in Python.

Add Column to a NumPy Array With the numpy.append() Function

The numpy.append() function can be used to add an extra column to an existing numpy array. The numpy.append() function takes three parameters, the pre-existing array, the new values to be added, and the axis by which we want to append the new values to the pre-existing array. We can specify the axis parameter to 1 if we want to add new columns to the pre-existing array. The numpy.append() function returns a new array in which the new values are appended at the end of the pre-existing array. See the following code example.

import numpy as np

array = np.array([[1, 2], [3, 4], [5, 6]])
array2 = np.append(array, [[1], [1], [1]], axis=1)
array2

Output:

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

In the above code, we first initialized our first array array with the numpy.array() function in Python. We then initialized a new array, array2, containing an extra column, with the numpy.append() function in Python.