Python one-way loop linked list

Operation

• Is_empty () Determine if the linked list is empty
• Length () returns the lengths of the linked list
• Travel () traversal
• Add (item) adds a node to the head
• Append (item) Adds a node to the tail
• Insert (POS, item) adds a node at the specified location pos
• Remove (item) deletes a node
• Search (item) to find out if the node exists

ClassNode (object):"""node"""    def __init__(self, item): Self.item=Item Self.next=NoneclassSincyclinkedlist (object):"""one-way circular linked list"""    def __init__(self): Self._head=NonedefIs_empty (self):"""determine if the linked list is empty"""        returnSelf._head = =NonedefLength (self):"""returns the length of the linked list"""        #returns the length 0 if the linked list is empty        ifself.is_empty ():return0 Count= 1cur=Self._head whileCur.next! =Self._head:count+ = 1cur=Cur.nextreturnCountdefTravel (self):"""traversing a linked list"""        ifself.is_empty ():returncur=Self._headPrintCur.item, whileCur.next! =Self._head:cur=Cur.nextPrintCur.item,Print ""    defAdd (Self, item):"""Adding a node to the head"""node=Node (item)ifself.is_empty (): Self._head=node Node.next=Self._headElse:            #added nodes point to _headNode.next =Self._head#move to the tail of the list and point to the next nodeCur =Self._head whileCur.next! =Self._head:cur=Cur.next Cur.next=node#_head point to add nodeSelf._head =nodedefAppend (self, item):"""Trailing Add node"""node=Node (item)ifself.is_empty (): Self._head=node Node.next=Self._headElse:            #move to the tail of the listCur =Self._head whileCur.next! =Self._head:cur=Cur.next#point the tail node to nodeCur.next =node#point node to head _headNode.next =Self._headdefInsert (self, POS, item):"""Add a node at the specified location"""        ifPOS <=0:self.add (item)elifPOS > (Self.length ()-1): Self.append (item)Else: Node=Node (item) cur=Self._head Count=0#move to the previous position in the specified position             whileCount < (pos-1): Count+ = 1cur=Cur.next Node.next=Cur.next Cur.next=nodedefRemove (self, item):"""Delete a node"""        #If the linked list is empty, return directly        ifself.is_empty ():return        #Point cur to the head nodeCur =Self._head Pre=None#if the element of the head node is the element to be found, item        ifCur.item = =Item:#If a linked list has more than one node            ifCur.next! =Self._head:#Find the tail node and point next to the second node                 whileCur.next! =Self._head:cur=Cur.next#cur points to the tail nodeCur.next =Self._head.next Self._head=Self._head.nextElse:                #A linked list has only one nodeSelf._head =NoneElse: Pre=Self._head#The first node is not the one you want to delete             whileCur.next! =Self._head:#the element to delete was found                ifCur.item = =Item:#DeletePre.next =Cur.nextreturn                Else: Pre=cur cur=Cur.next#cur pointing to the tail node            ifCur.item = =Item:#trailing DeletePre.next =Cur.nextdefSearch (self, item):"""find whether a node exists"""        ifself.is_empty ():returnFalse cur=Self._headifCur.item = =Item:returnTrue whileCur.next! =Self._head:cur=Cur.nextifCur.item = =Item:returnTruereturnFalseif __name__=="__main__": LL=sincyclinkedlist () Ll.add (1) Ll.add (2) Ll.append (3) Ll.insert (2, 4) Ll.insert (4, 5) Ll.insert (0,6)    Print "Length:", Ll.length () ll.travel ()PrintLl.search (3)    PrintLl.search (7) Ll.remove (1)    Print "Length:", Ll.length () ll.travel ()

Python one-way loop linked list