Two City Scheduling LeetCode challenge June Day 3

PYTHON CODE:
class Solution:
     def twoCitySchedCost(self, costs: List[List[int]]) -> int:
         summ = 0
         costs = sorted(costs,key = lambda a:a[0]-a[1])
         for i in range(len(costs)):
             if i < len(costs)//2:
                  summ+=costs[i][0]
             else:
                  summ+=costs[i][1]
          return summ