class iterativeMean:
    mean = None
    numberOfElementsInMean = 0

    def add(self, element):
        if self.mean is None:
            self.mean = element
        else:
            self.mean = ((self.mean * self.numberOfElementsInMean) + element) / (self.numberOfElementsInMean + 1)
        self.numberOfElementsInMean += 1