def insert(self, node, value): 'insert valut after node specified' t = Node(value) n = node.next if n is not None: t.next = n n.pre = t node.next = t t.pre = node return node
def append(self, value): if self.__first is None and self.__last is None: self._first = Node(value) self.__last = self.__first elif self.__first == self.__last: n = Node(value) self.__last = n self.__last.pre = self.__first self.__first.next = self.__last else: n = Node(value) self.__last.next = n n.pre = self.__last self.__last = n