new_contents: class Solution(object):
      def singleNonDuplicate(self, nums):
          """
          :type nums: List[int]
          :rtype: int
          """
          ln = len(nums)
          L, U = -1, ln
          while L + 1 < U:
              mid = L + (U - L) / 2
              if mid == ln - 1:
                  return nums[mid]
              other = mid / 2 * 2 + 1 - (mid % 2)
              if nums[other] == nums[mid]:
                  L = mid
              else:
                  U = mid
          return nums[U / 2 * 2]
  
subject: Add py solution for 540. Single Element in a Sorted Array