Circularly Doubly Linked List

CircularlyDoublyLinkedList (DoublyLinkedList)

A circularly doubly linked list is a cyclic collection of nodes whose head and tail nodes are connected. Each node contains a reference to the node preceding it, and a reference to the node succeeding it.

Instantiate a circularly doubly linked list object

>>> a_list = CircularlyDoublyLinkedList()

Append an item to the list

>>> a_list.append(0)

The L.append(x) method is an alias of L.insert_last(x)

>>> a_list.insert_last(1)

Insert an item at the head of the list

>>> a_list.insert_first(2)

Insert an item at a specific index

>>> a_list.insert(1, 3)

Insert an item at an index that's out of range raises IndexError

>>> a_list.insert(100, 3)
Traceback (most recent call last):
...
IndexError: Index out of range

Get first item of the list

>>> a_list.get_first()
2

Get first item of an empty list raises Empty

>>> CircularlyDoublyLinkedList().get_first()
Traceback (most recent call last):
...
linked_list.Empty: List is empty

Get last item of the list

>>> a_list.get_last()
1

Get last item of an empty list raises Empty

>>> CircularlyDoublyLinkedList().get_last()
Traceback (most recent call last):
...
linked_list.Empty: List is empty

Get item at a specific index

>>> a_list[1]
3

Get item at an index that's out of range raises IndexError

>>> a_list[100]
Traceback (most recent call last):
...
IndexError: Index out of range

Get items at slice range of the list

>>> a_list[1:3]
[3, 0]

Get items at a slice that's out of range raises IndexError

>>> a_list[1:100]
Traceback (most recent call last):
...
IndexError: Index out of range

Get items at a slice with a slice step of less than one raises a ValueError

>>> a_list[1:3:0]
Traceback (most recent call last):
...
ValueError: Step needs to be greater than zero

Get an iterable object of the list

>>> iterable_object = iter(a_list)

Get next item of the iterable object

>>> next(iterable_object)
2

Get next item of the list iterator

>>> next(a_list)
3

Get length of the the list

>>> len(a_list)
4

Get a string representation of the list

>>> str(a_list)
'[2, 3, 0, 1]'
>>> a_list
[2, 3, 0, 1]

Delete first item of the list

>>> a_list.remove_first()

Delete first item of an empty list raises Empty

>>> CircularlyDoublyLinkedList().remove_first()
Traceback (most recent call last):
...
linked_list.Empty: List is empty

Delete last item of the list

>>> a_list.remove_last()

Delete last item of an empty list raises Empty

>>> CircularlyDoublyLinkedList().remove_last()
Traceback (most recent call last):
...
linked_list.Empty: List is empty

Delete item at a specific index

>>> del a_list[0]

Delete item of at an index that's out of range raises IndexError

>>> del a_list[100]
Traceback (most recent call last):
...
IndexError: Index out of range

Replace item at a specific index

>>> a_list[0] = 100

Replace item of at an index that's out of range raises IndexError

>>> a_list[100] = 100
Traceback (most recent call last):
...
IndexError: Index out of range

Delete all items from the list

>>> a_list.remove_all()
>>> a_list
[]