class Buffer:
    def __init__(self):
        self.b = list()
    def add(self, *a):
        self.b.extend(a)
        print(sum(self.b[-5:]))
    def get_current_part(self):
        return self.b

buf = Buffer()
buf.add(1, 2, 3)
buf.get_current_part()
buf.add(4, 5, 6)
buf.get_current_part()