Better way to shuffle two related lists

Question

Is there better ways to randomly shuffle two related lists without breaking their correspondence in the other list? I\'ve found related questions in numpy.array

Answer 1

So far, all solutions created new lists in order to solve the problem. If the lists a and b are very long you may want to shuffle them in place. For that you would need a function like:

import random

def shuffle(a,b):
    assert len(a) == len(b)
    start_state = random.getstate()
    random.shuffle(a)
    random.setstate(start_state)
    random.shuffle(b)

a = [1,2,3,4,5,6,7,8,9]
b = [11,12,13,14,15,16,17,18,19]
shuffle(a,b)
print(a) # [9, 7, 3, 1, 2, 5, 4, 8, 6]
print(b) # [19, 17, 13, 11, 12, 15, 14, 18, 16]