NumPy Reference: 

Note: The expression a < mean produces a boolean array, like:

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

 

def filter():    a = np.array([        (20,20,10,23,26,32,10,5,0),        (0,2,50,20,0,1,28,5,0)    ])    mean = a.mean()    print("mean",mean) #14.0    print(a[a