a = np.arange(10)
b = np.arange(10)
#simple case
a[a<6] #array([0, 1, 2, 3, 4, 5])
# advanced case
mask = (a<6) & (b>4)
a[mask] #array([5])
mask * a #array([0, 0, 0, 0, 0, 5, 0, 0, 0, 0])a = np.arange(10)
b = np.arange(10)
#simple case
a[a<6] #array([0, 1, 2, 3, 4, 5])
# advanced case
mask = (a<6) & (b>4)
a[mask] #array([5])
mask * a #array([0, 0, 0, 0, 0, 5, 0, 0, 0, 0])