Insertion and Deletion in Circular Linked List in DSA Python

Program 1

# Implemenation of Circular linked list 
class Node:
    def __init__(self):
         self.data=None
         self.add=None

class CircularLinkedList:
     def __init__(self):
           self.start=None
           self.count=0

           # create list
     def createList(self):
          n=int(input("Enter an element"))
          self.start=Node()
          self.start.data=n
          self.start.add=self.start
          temp=self.start
          self.count=self.count+1
          choice=input("Want to continue")
          while(choice=="Y" or choice=="y"):
                n=int(input("Enter next element"))
                newnode=Node()
                newnode.data=n
                newnode.add=self.start
                temp.add=newnode
                temp=temp.add
                self.count=self.count+1
                choice=input("Want to continue")
# Display list
     def displayList(self):
          if(self.start==None):
                print("List not found")
          else:
                temp=self.start
                while(True):
                      print(temp.data,end=" ")
                      temp=temp.add
                      if(temp==self.start):
                            break
                print("\nTotal Node is : ",self.count)   
# insert first node
     def insertFirst(self):
           if(self.start==None):
                 print("List not found")
           else:
                 n=int(input("Enter an element"))
                 newnode=Node() 
                 newnode.data=n
                 newnode.add=None
                 last=self.start
                 while(last.add!=self.start):
                       last=last.add
                 newnode.add=self.start
                 self.start=newnode
                 last.add=self.start        
                 self.count=self.count+1               
# insert last node
     def insertLast(self):
           if(self.start==None):
                 print("List not found")
           else:      
                 n=input("Enter an element for insert")
                 newnode=Node()
                 newnode.data=n
                 newnode.add=None
                 last=self.start
                 while(last.add!=self.start):
                       last=last.add
                 last.add=newnode
                 newnode.add=self.start   
                 self.count=self.count+1                     

 # insert middle node
     def insertMiddle(self):
        if(self.start==None):
              print("List is empty")
        else:
            n=int(input("Enter an element for insert"))
            newnode=Node()
            newnode.data=n
            newnode.add=None
            pos=int(input("Enter the position"))
            if(pos>self.count):
                 print("Invalid position")
            else:     
                i=1
                next=self.start
                while(i<pos):
                     prev=next
                     next=next.add
                     i=i+1
                prev.add=newnode
                newnode.add=next                 
                self.count=self.count+1
    
 # delete first node
     def deleteFirst(self):
           if(self.start==None):
                 print("List not found")
           else:
                 last=self.start
                 while(last.add!=self.start):
                       last=last.add
                 temp=self.start
                 self.start=self.start.add      
                 last.add=self.start

                 print("Deleted node is: ",temp.data)
                 temp.add=None
                 temp=None   
                 self.count=self.count-1
           

     # Delete node from Middle  
     def deleteMiddle(self): 
        if(self.start==None):
              print("List is empty")
        else:
          pos=int(input("Enter the position for delete"))   
          if(pos>self.count):
               print("Invalid position")
          else:
               i=1
               next=self.start
               while(i<pos):
                    prev=next
                    next=next.add
                    i=i+1

               temp=next  
               next=next.add                   
               prev.add=next
               print("Deleted node is: ",temp.data)
               temp=None
               self.count=self.count-1

    # delete last node
     def deleteLast(self):
          if(self.start==None):
               print("List not found")
          else:
               last=self.start
               while(last.add!=self.start):
                     prev=last
                     last=last.add

               prev.add=self.start          
               print("Deleted Node is :",last.data)
               last.add=None
               last=None
               self.count=self.count-1

            

# Main Method
mylist=CircularLinkedList()
while(1):
    print("\n----------------------Circular Linked List Menu--------------\n")
    print("1.Create")
    print("2.Display")
    print("3.Insert First")
    print("4.Insert Middle")
    print("5.Insert Last")
    print("6.Delete First")
    print("7.Delete Middle")
    print("8.Delete Last")
    print("9.Exit")
    print("\n------------------------------------------------------------\n")
    choice=int(input("Enter your choice"))
    if(choice==1):
          mylist.createList()
    elif(choice==2):
          mylist.displayList()
    elif(choice==3):
          mylist.insertFirst()
    elif(choice==4):
          mylist.insertMiddle()      
    elif(choice==5):
          mylist.insertLast()      
    elif(choice==6):
          mylist.deleteFirst()
    elif(choice==7):
          mylist.deleteMiddle()
    elif(choice==8):
          mylist.deleteLast()          
    else:
         break