import functools

class Solution:

    # @param {integer[]} nums

    # @return {string}

    def largestNumber(self, nums):

        def comparator(x, y):   # inputs are string representations of non-negative ints

            if x+y > y+x:       # no need to convert to int because x+y and y+x are same length

                return -       # so lexicographic string sort behaves like numeric sort

            else:

                return 

        nums = list(map(str, nums))     # convert to strings

        nums.sort(key=functools.cmp_to_key(comparator))

        return nums

ls=[,,,,,]

x=Solution()

print(x.largestNumber(ls))

['', '', '', '', '', '']

[Program finished]