to complete the code for double linked list.

only the DLinkedList class to be completed as instructions given in the comments.

class DLinkedListNode:

# An instance of this class represents a node in Doubly-Linked List

def __init__(self,initData,initNext,initPrevious):

self.data = initData

self.next = initNext

self.previous = initPrevious

if initNext != None:

self.next.previous = self

if initPrevious != None:

self.previous.next = self

def getData(self):

return self.data

def setData(self,newData):

self.data = newData

def getNext(self):

return self.next

def getPrevious(self):

return self.previous

def setNext(self,newNext):

self.next = newNext

def setPrevious(self,newPrevious):

self.previous = newPrevious

class DLinkedList:

# An instance of this class represents the Doubly-Linked List

def __init__(self):

self.__head=None

self.__tail=None

self.__size=0

def search(self, item):

current = self.__head

found = False

while current != None and not found:

if current.getData() == item:

found= True

else:

current = current.getNext()

return found

def index(self, item):

current = self.__head

found = False

index = 0

while current != None and not found:

if current.getData() == item:

found= True

else:

current = current.getNext()

index = index + 1

if not found:

index = -1

return index

def add(self, item):

# TODO:adds a new node (containing the item as its data) to the head of the list.

pass

def remove(self, item):

# TODO:removes the first element in the list that is equal to item. If the item is not in the list, the list is not changed and an exception should NOT be raised.

pass

def append(self, item):

# TODO:adds a new node (containing the item as its data) to the tail of the list.

pass

def insert(self, pos, item):

# TODO:adds a new node (containing the item as its data) at the given position in the list. For example, if pos is 0, then the new node goes at the beginning (head) of the list. pos must be an integer, and for this exercise, cannot be negative.

pass

def pop1(self):

# TODO: removes and returns the last item from the list

pass

def pop(self, pos=None):

# TODO: removes and returns the item in the given position. An error should be raised if the position is outside of the list. pos must be an integer, and for this exercise, cannot be negative.

# Hint - incorporate pop1 when no pos argument is given

pass

def searchLarger(self, item):

# TODO: returns the position of the first element that is larger than item, or -1 if there is no larger item.

pass

def getSize(self):

# TODO:returns the number of elements in the list.

pass

def getItem(self, pos):

# TODO:returns the item at the given position. An exception should be raised if the position is outside of the list. pos must be an integer, and it can be positive OR negative.

pass

def __str__(self):

# TODO:returns a string of the elements in the doubly-linked list, with one space in between each element.

pass

def test():

linked_list = DLinkedList()

is_pass = (linked_list.getSize() == 0)

assert is_pass == True, "fail the test"

linked_list.add("World")

linked_list.add("Hello")

is_pass = (str(linked_list) == "Hello World")

assert is_pass == True, "fail the test"

is_pass = (linked_list.getSize() == 2)

assert is_pass == True, "fail the test"

is_pass = (linked_list.getItem(0) == "Hello")

assert is_pass == True, "fail the test"

is_pass = (linked_list.getItem(1) == "World")

assert is_pass == True, "fail the test"

is_pass = (linked_list.getItem(0) == "Hello" and linked_list.getSize() == 2)

assert is_pass == True, "fail the test"

is_pass = (linked_list.pop(1) == "World")

assert is_pass == True, "fail the test"

is_pass = (linked_list.pop() == "Hello")

assert is_pass == True, "fail the test"

is_pass = (linked_list.getSize() == 0)

assert is_pass == True, "fail the test"

int_list2 = DLinkedList()

for i in range(0, 10):

int_list2.add(i)

int_list2.remove(1)

int_list2.remove(3)

int_list2.remove(2)

int_list2.remove(0)

is_pass = (str(int_list2) == "9 8 7 6 5 4")

assert is_pass == True, "fail the test"

for i in range(11, 13):

int_list2.append(i)

is_pass = (str(int_list2) == "9 8 7 6 5 4 11 12")

assert is_pass == True, "fail the test"

for i in range(21, 23):

int_list2.insert(0,i)

is_pass = (str(int_list2) == "22 21 9 8 7 6 5 4 11 12")

assert is_pass == True, "fail the test"

is_pass = (int_list2.getSize() == 10)

assert is_pass == True, "fail the test"

int_list = DLinkedList()

is_pass = (int_list.getSize() == 0)

assert is_pass == True, "fail the test"

for i in range(0, 1000):

int_list.append(i)

correctOrder = True

is_pass = (int_list.getSize() == 1000)

assert is_pass == True, "fail the test"

for i in range(0, 200):

if int_list.pop() != 999 - i:

correctOrder = False

is_pass = correctOrder

assert is_pass == True, "fail the test"

is_pass = (int_list.searchLarger(200) == 201)

assert is_pass == True, "fail the test"

int_list.insert(7,801)

is_pass = (int_list.searchLarger(800) == 7)

assert is_pass == True, "fail the test"

is_pass = (int_list.getItem(-1) == 799)

assert is_pass == True, "fail the test"

is_pass = (int_list.getItem(-4) == 796)

assert is_pass == True, "fail the test"

if is_pass == True:

print ("=========== Congratulations! Your have finished exercise 2! ============")

if __name__ == '__main__':

test()