np.sort(students, order=['class', 'height'])
np.array(students_details, dtype=data_type)
'name', 'S15'
'class', int
'height', float
'James', 5, 48.5
'Nail', 6, 52.5
'Paul', 5, 42.10
'Pit', 5, 40.11
data_type
students_details
Original array
b'James', 5, 48.5
b'Nail', 6, 52.5
b'Paul', 5, 42.1
b'Pit', 5, 40.11
Sort by class, then height if class are equal
b'Pit', 5, 40.11
b'Paul', 5, 42.1
b'James', 5, 48.5
b'Nail', 6, 52.5
Class are equal, so sort by height