def insert_first(self, value):
node_value = DoublyNode(value)
node_value.next = self.head.next
node_value.previous = self.head
node_value.next.previous = node_value
self.head.next = node_value
self.__length += 1
def insert_last(self, value):
node_value = DoublyNode(value)
node_value.previous = self.tail.previous
node_value.next = self.tail
node_value.previous.next = node_value
self.tail.previous = node_value
self.__length += 1
def insert_at(self, value, position):
if position < 1:
return self.insert_first(value)
if position >= len(self):
return self.insert_last(value)
new_node = DoublyNode(value)
position_node = self.__get_node_at(position)
new_node.next = position_node
new_node.previous = position_node.previous
new_node.previous.next = new_node
position_node.previous = new_node
self.__length += 1
def __init__(self):
self.head = DoublyNode("HEAD")
self.tail = DoublyNode("TAIL")
self.head.next = self.tail
self.tail.previous = self.head
self.__length = 0
def get_element_at(self, position):
value_returned = None
value_to_be_returned = self.__get_node_at(position)
if value_to_be_returned:
value_returned = DoublyNode(value_to_be_returned.value)
return value_returned