numpy find index of matching values

1import numpy as np
2# init arrays
3a = np.array([1,2,3,2,3,4,3,4,5,6])
4b = np.array([7,2,10,2,7,4,9,4,9,8])
5
6#using enumerate, list comprehension and set
7print([key for key, val in enumerate(a) if val in set(b)])
8# output
9# [1, 3, 5, 7]
10