two Python question about Cirlist class

1.Extend the Circular LinkedList class CirList by adding the __str__(self) method that returns a reasonable string representation of an ordered list using space and square brackets.

The implementations of the NodeDLL is provided to you as part of this exercise. You can simply use: NodeDLL(), get_prev(), get_next(), set_prev(), set_next(), as well as get_data() and set_data() as necessary in your function definition. Note: You should include the entire Circular LinkedList class definition in your answer to this question.

For example:

Test	Result
listA = CirList() listA.append(5) listA.append(3) listA.append(3) print(listA)	[5 3 3]

2.Extend the Circular LinkedList class CirList by adding the __str__(self) method that returns a reasonable string representation of an ordered list using space and square brackets. You are also asked to re-write the append(self, item) and add_before(self, item, old_item) methods such that no duplicate items will be appeared on the ordered list.

The implementations of the NodeDLL is provided to you as part of this exercise. You can simply use: NodeDLL(), get_prev(), get_next(), set_prev(), set_next(), as well as get_data() and set_data() as necessary in your function definition. Note: You should include the entire Circular LinkedList class definition in your answer to this question.

For example:

Test	Result
listA = CirList() listA.append(5) listA.append(3) listA.append(3) print(listA)	[5 3]

and here are my codes of node and cirlist :

class NodeDLL:

def __init__(self, init_data, next_node=None, prev_node=None):

self.data = init_data

self.next = next_node

self.prev = prev_node

def get_data(self):

return self.data

def get_prev(self):

return self.prev

def get_next(self):

return self.next

def set_data(self, new_data):

self.data = new_data

def set_next(self, new_next):

self.next = new_next

def set_prev(self, new_prev):

self.prev = new_prev

class CirList:

def __init__(self):

head_node = NodeDLL(None)

head_node.next = head_node

head_node.prev = head_node

self.__head = head_node

def append(self, item):

curr = self.__head

new_node = NodeDLL(item, curr, curr.get_prev())

curr.set_prev(new_node)

new_node.get_prev().set_next(new_node)

def add_before(self, item, old_item):

curr = self.__head.next

found = False

while curr.get_data() != None and not found:

if curr.get_data() == old_item:

found = True

else:

curr = curr.get_next()

if found:

new_node = NodeDLL(item, curr, curr.get_prev())

curr.set_prev(new_node)

new_node.get_prev().set_next(new_node)

return found

def remove(self, item):

curr = self.__head.next

found = False

while curr.get_data() != None and not found:

if curr.get_data() == item:

found = True

else:

curr = curr.get_next()

if found:

curr.get_prev().set_next(curr.get_next())

curr.get_next().set_prev(curr.get_prev())

def printall(self):

curr = self.__head.next

while curr.get_data() != None:

print(curr.get_data(), end=" ")

curr = curr.get_next()

print()