beginning to end is identical to that with singly linked list we start at the node referenced by head and advance the temporary referencecurnodeone node at timeusing the next link field the reverse traversalprovided in listing starts at the node referenced by tail and advances curnodeone node at timeusing the prev link field in either casethe traversal terminates when curnode is set to nullresulting in (nlinear time operation listing traversing doubly linked list in reverse order def revtraversaltail )curnode tail while curnode is not none printcurnode data curnode curnode prev searching searching for specific item in doubly linked listbased on key valuecan be implemented in the same fashion as for singly linked list start with the first node and iterate through the list until we find the target item or we encounter node containing key value larger than the target but doubly linked list provides an advantage not available in the singly linked list since we can move forward or backwardthe search operations do not have to begin with the first node suppose we perform sequence of search operations on the list from figure and we begin that sequence with search for value using the external reference probe to iterate through the listthe target is found in the third node if we leave probe pointing to the third nodeas illustrated in figure we can begin the next search operation where the previous search left off instead of starting over from the beginning suppose the next search is for value we can compare this target value to the item currently referenced by probe and determine if the search should proceed forward or backward starting from the probe node in this casewe search backwardusing probe to traverse the list thuseach time search is performedwe leave the probe reference where the previous search ended and use it for subsequent searches note that probe is not temporary reference variable as curnode was in the normal search operationbut must be maintained between operations in the same fashion as head and tail given the three external head probe tail figure probe reference positioned after searching for value