Flip or reverse columns in numpy array

Question

I want to flip the first and second values of arrays in an array. A naive solution is to loop through the array. What is the right way of doing this?

import numpy as np
contour = np.array([[1, 4],
                    [3, 2]])

flipped_contour = np.empty((0,2))
for point in contour:
    x_y_fipped = np.array([point[1], point[0]])
    flipped_contour = np.vstack((flipped_contour, x_y_fipped))

print(flipped_contour)

[[4. 1.]
[2. 3.]]

Answer 1

Use the aptly named np.flip:

np.flip(contour, axis=1)

Or,

np.fliplr(contour)

array([[4, 1],
       [2, 3]])

Answer 2

You can use numpy indexing:

contour[:, ::-1]