Remove elements from one array if present in another array, keep duplicates - NumPy / Python

Question

I have two arrays A (len of 3.8million) and B (len of 20k). For the minimal example, lets take this case:

A = np.array([1,1,2,3,3,         


        

Answer 1

I am not very familiar with numpy, but how about using sets:

C = set(A.flat) - set(B.flat)

EDIT : from comments, sets cannot have duplicates values.

So another solution would be to use a lambda expression :

C = np.array(list(filter(lambda x: x not in B, A)))