class CircularQueue:

    class __Node:
        def __init__(self, value):
            self.value = value
            self.next = self.prev = None

    def __init__(self):
        self.front = self.rear = None

    def enqueue(self, value):
        if self.front is None and self.rear is None:
            newNode = CircularQueue.__Node(value)
            self.front = self.rear = newNode
        elif self.rear is not None:
            newNode = CircularQueue.__Node(value)
            self.__enqueue(newNode, self.front)
            self.rear = newNode

    def __enqueue(self, node, cur_node):
        if cur_node.next is None:
            cur_node.next = node
            node.prev = cur_node
            return
        else:
            self.__enqueue(node, cur_node.next)

    def dequeue(self):
        if self.front is None:
            print('No data available for dequeue!')
        elif self.front.next is not None:
            self.front.next.prev = None
            front = self.front
            del self.front
            self.front = front.next
            del front
        elif self.front.next is None:
            del self.front
            self.front = self.rear = None

    def showQueue(self):
        if self.front is None:
            print('No data available for showing!')
        else:
            return self.__showQueue(self.front)

    def __showQueue(self, cur_node):
        if cur_node is None:
            return
        else:
            print(cur_node.value)
            self.__showQueue(cur_node.next)


    def getFront(self):
        return self.front

    def isempty(self):
        return self.front == self.rear

queue = CircularQueue()

queue.enqueue(10)
queue.enqueue(20)
queue.dequeue()
queue.enqueue(30)
queue.dequeue()
queue.enqueue(40)
queue.enqueue(50)

queue.showQueue()
# OUTPUT:-
# 30
# 40
# 50