Leetcode: Two Sum @Python

class Solution:
    # @return a tuple, (index1, index2)
    def twoSum(self, num, target):
        dict={}
        for i in range(len(num)):
            res=target-num[i]
            if res in dict:
                return (dict[res],i+1)
            else:
                dict[num[i]]=i+1
        return (-1,-1)