python sorting two lists

Question

I am trying to sort two lists together:

list1 = [1, 2, 5, 4, 4, 3, 6]
list2 = [3, 2, 1, 2, 1, 7, 8]

list1, list2 = (list(x) for x in zip(*sorted(zip(list1,          


        

Answer 1

Use a key parameter for your sort that only compares the first element of the pair. Since Python's sort is stable, this guarantees that the order of the second elements will remain the same when the first elements are equal.

>>> from operator import itemgetter
>>> [list(x) for x in zip(*sorted(zip(list1, list2), key=itemgetter(0)))]
[[1, 2, 3, 4, 4, 5, 6], [3, 2, 7, 2, 1, 1, 8]]

Which is equivalent to:

>>> [list(x) for x in zip(*sorted(zip(list1, list2), key=lambda pair: pair[0]))]
[[1, 2, 3, 4, 4, 5, 6], [3, 2, 7, 2, 1, 1, 8]]