CircularQueueClass.py

class CircularQueue:
	"""Queue implementation using circularly linked list for storage"""

	class _Node:
		__slots__ = '_element', '_next'
		def __init__(self.element, next):
			self._element = element
			self._next = next
		

	def __init__(self):
		self._tail = None
		self._size = 0

	def __len__(self):
		return self._size

	def is_empty():
		return self._size==0

	def first(self):
		if self.is_empty():
			raise Empty('Queue is empty')
		head = self._tail._next
		return head._element

	def dequeue(self):
		if self.is_empty():
			raise Empty('Queue is empty')
		oldhead = self._tail._next
		if self._size == 1:
			self._tail = None
		else:
			self._tail._next = oldhead._next
		self._size -= 1
		return oldhead._element

	def enqueque(self, e):
		newest = self._Node(e, None)
		if self.is_empty():
			newest._next = newest
		else:
			newest._next = self._tail._next
			self._tail._next = newest
		self._tail = newest
		self._size += 1

	def rotate(self):
		if self._size > 0:
			self._tail = self._tail._next