reverse a doubly circular linked list by swapping node value in python

Python program for reverse a doubly circular linked list by swapping node value. Here problem description and explanation.

#  Python 3 Program
#  Reverse a doubly circular linked list by swapping value

#  Linked list node
class LinkNode :
	def __init__(self, data, back, next) :
		self.data = data
		self.back = back
		self.next = next
	

class CircularDoublyLL :
	def __init__(self) :
		self.front = None
		self.tail = None
	
	#  Add new node at the end of linked list
	def addNode(self, data) :
		node = LinkNode(data, None, None)
		#  When new node is successfully created
		if (self.front == None) :
			#  Add first node of linked list
			self.front = node
			self.tail = node
		else :
			#  Add node at last position
			self.tail.next = node
			node.back = self.tail
			self.tail = node
		
		#  Connect the last node in the linked list to front
		self.tail.next = self.front
		self.front.back = self.tail
		#  Set node data
		node.data = data
	
	#  Print linked list nodes
	def printElement(self) :
		if (self.front == None) :
			print("\n Empty Linked List ")
		else :
			temp = self.front
			print("\n Linked List from Front to Tail ")
			#  Display doubly linked list from start to last node
			while (temp != None) :
				print("",temp.data, end = " ")
				if (temp == self.tail) :
					#  When get last node
					temp = None
				else :
					temp = temp.next
				
			
			temp = self.tail
			print("\n Linked List from Tail to Front ")
			#  Display doubly linked list from last to start node
			while (temp != None) :
				print("",temp.data, end = " ")
				if (temp == self.front) :
					#  When get first node
					temp = None
				else :
					temp = temp.back
				
			
		
	
	#  Reverses the elements of doubly linked list
	#  using swap node values
	def reverseElement(self) :
		#  Get first node
		first = self.front
		#  Get last node
		last = self.tail
		temp = 0
		#  Reverse operation
		while (first != None and last != None) :
			if (first != last) :
				#  Swap the node value
				temp = first.data
				first.data = last.data
				last.data = temp
				if (first.next == last) :
					#  Stop reverse operation, or use break
					first = None
					last = None
				else :
					first = first.next
					last = last.back
				
			else :
				#  Stop reverse operation, or use break
				first = None
				last = None
			
		
	

def main() :
	cll = CircularDoublyLL()
	#  Add linked list node
	cll.addNode(1)
	cll.addNode(2)
	cll.addNode(3)
	cll.addNode(4)
	cll.addNode(5)
	cll.addNode(6)
	print("\n Before reverse linked list", end = "")
	cll.printElement()
	cll.reverseElement()
	print("\n\n After reverse linked list", end = "")
	cll.printElement()

if __name__ == "__main__": main()

Output

 Before reverse linked list
 Linked List from Front to Tail
 1  2  3  4  5  6
 Linked List from Tail to Front
 6  5  4  3  2  1

 After reverse linked list
 Linked List from Front to Tail
 6  5  4  3  2  1
 Linked List from Tail to Front
 1  2  3  4  5  6