Find First & Last Position of Element in Sorted Array

class Solution:
    def searchRange(self, nums: List[int], target: int) -> List[int]:

        def upper_bound(nums: List[int], target:int):
            """Returns the index of last element"""
            low, high = 0, len(nums)-1
            result = -1

            while (low <= high):
                mid = (low + high)//2
                if nums[mid] <= target:
                    result = mid
                    low = mid + 1
                else:
                    high = mid - 1

            if result != -1 and nums[result] != target:
                return -1

            return result

        def lower_bound(nums: List[int], target:int):
            low, high = 0, len(nums)-1
            result = -1

            while (low <= high):
                mid = (low + high)//2
                if nums[mid] >= target:
                    result = mid
                    high = mid - 1
                else:
                    low = mid + 1

            if result != -1 and nums[result] != target:
                return -1

            return result

        start = lower_bound(nums, target)
        end = upper_bound(nums, target)

        return [start, end]