maxiumum average subarray I

class Solution:
    def findMaxAverage(self, nums: List[int], k: int) -> float:

        left = 0
        right = 0
        window_sum = 0
        max_window_sum = -float("inf")

        while right < len(nums):
            if nums[right] < k - 1:
                # keep adding until you expanded the
                # window enough
                window_sum = window_sum + nums[right]
                right += 1
            else:
                # add right most element assuming that left most
                # element is already inside the window
                window_sum = window_sum + nums[right]
                max_window_sum = max(window_sum, max_window_sum)

                # prepare for next iteration
                window_sum -= nums[left]
                left += 1
                right += 1

        return max_window_sum/(k*1.0)