Adding Extra Columns to a NumPy Array

Suppose you have a 2D NumPy array a as follows:

a = np.array([
    [1, 2, 3],
    [2, 3, 4],
])

To add a column of zeros along the second axis, you can utilize various methods. One approach is to employ the np.c_[ ] function:

b = np.c_[a, np.zeros(a.shape[0])]

This will create a new array b with an additional column of zeros:

b = np.array([
    [1, 2, 3, 0],
    [2, 3, 4, 0],
])

Alternatively, you can use the np.r_[ ] function:

b = np.r_[a, np.zeros((a.shape[0], 1))]

This method will also add a column of zeros to the array.

Note that np.r_[ ] and np.c_[ ] provide flexible options for modifying array dimensions. They can be utilized to mix vectors and scalars, add rows or columns, and even insert entire arrays at specified positions.