Flatten a folded linked list in python

Python program for Flatten a folded linked list. Here problem description and explanation.

#  Python 3 program for
#  Unfold a folded linked list OR
#  flatten folded linked list

#  Linked list node
class LinkNode :
	def __init__(self, data) :
		self.data = data
		self.next = None
	

class SingleLL :
	def __init__(self) :
		self.head = None
	
	#  Insert node at the beginning of linked list
	def addNode(self, data) :
		#  Create node
		node = LinkNode(data)
		node.next = self.head
		#  Set new head
		self.head = node
	
	#  Display linked list element
	def display(self) :
		if (self.head == None) :
			return
		
		temp = self.head
		#  iterating linked list elements
		while (temp != None) :
			print("", temp.data , end = " →")
			#  Visit to next node
			temp = temp.next
		
		print(" NULL")
	
	#  This is handle the request of unfold given linked list nodes
	def unfoldList(self) :
		if (self.head == None) :
			print("\n Empty linked list")
			return
		
		temp = self.head
		auxiliary = None
		hold = None
		#  Loop which is separating the fold elements 
		while (temp.next != None) :
			#  Get the second element
			hold = temp.next
			if (hold.next != None) :
				#  When exists pair of three elements
				temp.next = hold.next
				#  Visit to 3rd element
				temp = hold.next
			else :
				#  When get last two elements
				temp.next = None
			
			#  Add new node at beginning of auxiliary linked list
			hold.next = auxiliary
			#  Make new head node
			auxiliary = hold
		
		if (temp != None) :
			#  Combine lists
			temp.next = auxiliary
		
	

def main() :
	#  Create a empty linked lists
	sll1 = SingleLL()
	sll2 = SingleLL()
	#   Constructed first linked list
	#   2 → 5 → 1 → 8 → 10 → 4 → 9 → 7 → NULL
	sll1.addNode(7)
	sll1.addNode(9)
	sll1.addNode(4)
	sll1.addNode(10)
	sll1.addNode(8)
	sll1.addNode(1)
	sll1.addNode(5)
	sll1.addNode(2)
	#  Constructed second linked list
	#  1 → 2 → 3 → 4 → 5 → 6 → 7 → NULL
	sll2.addNode(7)
	sll2.addNode(6)
	sll2.addNode(5)
	sll2.addNode(4)
	sll2.addNode(3)
	sll2.addNode(2)
	sll2.addNode(1)
	#  Test A
	print(" Before unfold")
	sll1.display()
	sll1.unfoldList()
	print(" After unfold")
	sll1.display()
	#  Test B
	print(" Before unfold")
	sll2.display()
	sll2.unfoldList()
	print(" After unfold")
	sll2.display()

if __name__ == "__main__": main()

Output

 Before unfold
 2 → 5 → 1 → 8 → 10 → 4 → 9 → 7 → NULL
 After unfold
 2 → 1 → 10 → 9 → 7 → 4 → 8 → 5 → NULL
 Before unfold
 1 → 2 → 3 → 4 → 5 → 6 → 7 → NULL
 After unfold
 1 → 3 → 5 → 7 → 6 → 4 → 2 → NULL