Implementation of bidirectional linked list of PYTHON--PYTHON data structure

Like a single-linked list, it just adds a pointer to the previous element.

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Python implementation code:

#Personal Python Data Structure--ppds##!/usr/bin/python#-*-coding:utf-8-*-classNode (object):def __init__(self,val,p=0): Self.data=Val Self.next=P Self.prev=Pclasslinklist (object):def __init__(self): Self.head=0definitlist (self,data): Self.head=Node (data[0]) p=Self.head forIinchData[1:]: node=Node (i) P.next=node Node.prev=P P=P.nextdefGetLength (self): length=0 P=Self.head whileP! =0:length+=1P=P.nextreturnlengthdefIs_empty (self):ifSelf.getlength () = =0:returnTrueElse:            returnFalsedefClear (self): Self.head=0defAppend (self,item): Q=Node (item)ifSelf.head = =0:self.head=QElse: P=Self.head whileP.next! =0:p=P.next P.next=Q Q.prev=PdefGetItem (self,index):ifself.is_empty ():Print('linklist is empty.')            returnJ=0 P=Self.head whileP.next! = 0 andJ <index:p=P.next J+=1ifj = =Index:returnP.dataElse:            Print('target is not exist!')    defInsert (Self,index,item):ifSelf.is_empty ()orIndex < 0orIndex >self.getlength ():Print('linklist is empty.')            return        ifindex = =0:q=Node (item,self.head) Self.head=Q J=0 P=Self.head Post=Self.head whileP.next! = 0 andJ <Index:post=P P=P.next J+=1ifindex = =J:q=Node (item,p) Post.next=Q Q.prev=Post Q.next=P P.prev=QdefDelete (self,index):ifSelf.is_empty ()orIndex < 0orIndex >self.getlength ():Print('linklist is empty.')            return        ifindex = =0:q=Node (item,self.head) Self.head=Q J=0 P=Self.head Post=Self.head whileP.next! = 0 andJ <Index:post=P P=P.next J+=1ifindex = =J:post.next=P.next P.next.prev=PostdefIndex (self,value):ifself.is_empty ():Print('linklist is empty.')            returnI=0 P=Self.head whileP.next! = 0 and  notP.data = =value:p=P.next i+=1ifP.data = =Value:returnIElse:            return-1if __name__=='__main__': L=linklist () llist=[7,3,10,4,5,] l.initlist (llist)Print(L.getlength ())Print(L.is_empty ())#L.append (one)    #L.insert (2,100)    Print(L.getlength ())Print(L.getitem (0)) forIinchRange (L.getlength ()):Print(L.index (Llist[i])) l.clear ()Print(L.getlength ())

Implementation of bidirectional linked list of PYTHON--PYTHON data structure