class ValueWindow():
  def __init__(self, window_size=100):
    self._window_size = window_size
    self._values = []

  def append(self, x):
    self._values = self._values[-(self._window_size - 1):] + [x]

  @property
  def sum(self):
    return sum(self._values)

  @property
  def count(self):
    return len(self._values)

  @property
  def average(self):
    return self.sum / max(1, self.count)

  def reset(self):
    self._values = []