Move vowels node at the beginning of linked list in python

Python program for Move vowels node at the beginning of linked list. Here problem description and other solutions.

#  Python 3 program for
#  Shift the vowels node at beginning of 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
		self.tail = None
	
	#  Add new node at end of linked list 
	def addNode(self, data) :
		node = LinkNode(data)
		if (self.head == None) :
			self.head = node
		else :
			#  Append the node at last position
			self.tail.next = node
		
		self.tail = node
	
	#  Display linked list element
	def display(self) :
		if (self.head == None) :
			print("\n Empty linked list")
			return
		
		temp = self.head
		#  iterating linked list elements
		while (temp != None) :
			print("", temp.data ,end = " →")
			#  Visit to next node
			temp = temp.next
		
		print(" NULL")
	
	#  Determine that given value is an vowel or not
	def isVowels(self, value) :
		if (value == 'a'
			or value == 'e'
			or value == 'i'
			or value == 'o'
			or value == 'u'
			or value == 'A'
			or value == 'E'
			or value == 'I'
			or value == 'O'
			or value == 'U') :
			return True
		
		return False
	
	#  Move the vowels value at beginning position
	def shiftVowels(self) :
		if (self.head == None) :
			print("\n Empty linked list")
			return
		
		#  Define some auxiliary variable
		node = self.head
		back = None
		#  iterate linked list nodes
		#  And shift vowels at front of linked list
		while (node != None) :
			if (self.isVowels(node.data) == True and back != None) :
				#  Enter here when
				#  Node is contain vowel and 
				#  its previous (any) node is not form of vowel
				if (node == self.tail) :
					#  When is last node
					#  Set new last node
					self.tail = back
				
				#  Connect previous node to next node
				back.next = node.next
				#  Connect vowel node to first node
				node.next = self.head
				#  Set new head
				self.head = node
				#  Get back node
				node = back
			else :
				back = node
			
			#  Visit to next node
			node = node.next
		
	

def main() :
	sll = SingleLL()
	#  Constructed linked list
	sll.addNode('E')
	sll.addNode('D')
	sll.addNode('U')
	sll.addNode('C')
	sll.addNode('A')
	sll.addNode('T')
	sll.addNode('I')
	sll.addNode('O')
	sll.addNode('N')
	print(" Before move vowels")
	#  E → D → U → C → A → T → I → O → N → NULL
	sll.display()
	sll.shiftVowels()
	print(" After move vowels")
	#  O → I → A → U → E → D → C → T → N → NULL
	sll.display()

if __name__ == "__main__": main()

Output

 Before move vowels
 E → D → U → C → A → T → I → O → N → NULL
 After move vowels
 O → I → A → U → E → D → C → T → N → NULL