leetcode 645 Set Mismatch

python:

class Solution:
    def findErrorNums(self, nums):
        """
        :type nums: List[int]
        :rtype: List[int]
        """
        l = len(nums)
        res = []
        res.append(sum(nums) - sum(set(nums)))
        res.append(l*(1+l)//2 - sum(set(nums)))
        return res