Find the set difference between two large arrays (matrices) in Python

Question

I have two large 2-d arrays and I\'d like to find their set difference taking their rows as elements. In Matlab, the code for this would be setdiff(A,B,\'rows\')

Answer 1

I'm not sure what you are going for, but this will get you a boolean array of where 2 arrays are not equal, and will be numpy fast:

import numpy as np
a = np.random.randn(5, 5)
b = np.random.randn(5, 5)
a[0,0] = 10.0
b[0,0] = 10.0 
a[1,1] = 5.0
b[1,1] = 5.0
c = ~(a-b==0)
print c


[[False  True  True  True  True]
 [ True False  True  True  True]
 [ True  True  True  True  True]
 [ True  True  True  True  True]
 [ True  True  True  True  True]]