LeetCode Note Two Sum

I have tried two kinds of the algorithm.

1. Do sum by loop and check whether the sum is equal to the target

   for i in range(len(nums)):
       sumList = [nums[i]+item for item in nums[i+1:]]
       for sumNum in sumList:
           if sumNum == target:
               return [i, sumList.index(sumNum)+i+1]

2. Use the index() in List
   By using this, the performance become much better.

   for i in range(len(nums)):
       targetNum = target-nums[i]
       if targetNum in nums and nums.index(targetNum) != i:
           return i, nums.index(targetNum)