`numpy:union1d`

Signature

def union1d(ar1, ar2)

Find the union of two arrays.

Return the unique, sorted array of values that are in either of the two input arrays.

ar1, ar2 : array_like: Input arrays. They are flattened if they are not already 1D.

import numpy as np
np.union1d([-1, 0, 1], [-2, 0, 2])

✓

array([-2, -1,  0,  1,  2])

To find the union of more than two arrays, use functools.reduce:

from functools import reduce
reduce(np.union1d, ([1, 3, 4, 3], [3, 1, 2, 1], [6, 3, 4, 2]))

✓

array([1, 2, 3, 4, 6])