>>> import numpy as np
>>> A = np.array([3,4,6,10,24,89,45,43,46,99,100])
>>> A[A%3!=0]
array([ 4, 10, 89, 43, 46, 100])
>>> A[A%5==0]
array([ 10, 45, 100])
>>> A[(A%3==0) & (A%5==0)]
array([45])
>>> A[A%3==0] = 42
>>> A
array([ 42, 4, 42, 10, 42, 89, 42, 43, 46, 42, 100])
>>>