class DataBuffer(object):
    def __init__(self, length):
        self.__max = length
        self.__data = []

    def push(self, element):
        if self.__max == 0:
            return False
        if len(self.__data) == self.__max:
            _ = self.__data.pop(0)
        self.__data.append(element)
        return True

    def average(self):
        if len(self.__data) is 0:
            return None
        return sum(self.__data) / len(self.__data)

    def length(self):
        return len(self.__data)

    def clear(self):
        self.__data = []