Another Linked List

Table of Contents

• What is it?
• Why create it?
• Simple usage
• Api
  • class LinkedList([a list of elements])
    • Attributes
    • Methods
  • node
• Test

What is it?

• An incomprehensive implementation of a doubly-linked list

Why create it?

• I didn't like the api or documentation of other linked lists. I'm also new to python so this was a good way to learn.

Simple usage

from another_linked_list import LinkedList

# create a list with three nodes
ll = LinkedList(["a", "b", "d"])

# get the node with element "b"
bNode = ll.findFirstNode("b")

# insert "c" after bNode
ll.insertAfter(bNode, "c")

print(list(ll))
# prints ['a', 'b', 'c', 'd']

Api

class LinkedList([a list of elements])

• the linked list holds a list of nodes. Each node holds an element (the value) along with pointers to the previous and next nodes. For the most part the methods are intended to allow you to work with the elements moreso than the nodes because that was my use-case. This design decision may change in the future to be more focused around the nodes.
• all methods return self unless specified otherwise
• all methods which take a list argument also accept an instance of LinkedList
• in all code examples below, assume ll starts with LinkedList(["a", "c"])
• the internal methods implemented are
  • __copy__
  • __iter__ (iterates over the elements, not the nodes)
  • __len__
  • __reversed__

Attributes

firstNode: node

print(ll.firstNode.element) # a

lastNode: node

print(ll.lastNode.element) # c

Methods

append(element)

ll.append('d')
print(list(ll)) # ['a', 'c', 'd']

copy() => LinkedList

appendAll(list)

ll.appendAll(['d', 'e'])
print(list(ll)) # ['a', 'c', 'd', 'e']

findFirstNode(element) => node

cNode = ll.findFirstNode(['c'])
print(cNode.element) # c

insertAfter(node, element)

ll.insertAfter(ll.firstNode, 'b')
print(list(ll)) # ['a', 'b', 'c']

insertAllAfter(node, list)

ll.insertAllAfter(ll.firstNode, ['b', 'd'])
print(list(ll)) # ['a', 'b', 'd', 'c']

insertAllBefore(node, list)

ll.insertAllBefore(ll.lastNode, ['b', 'd'])
print(list(ll)) # ['a', 'b', 'd', 'c']

insertBefore(node, element)

ll.insertBefore(ll.lastNode, 'b')
print(list(ll)) # ['a', 'b', 'c']

prepend(element)

ll.prepend('z')
print(list(ll)) # ['z', 'a', 'c']

prependAll(list)

ll.prependAll(['y', 'z'])
print(list(ll)) # ['y', 'z', 'a', 'c']

removeFirstElement(element)

ll.removeFirstElement('c')
print(list(ll)) # ['a']

removeNode(node)

ll.removeNode(ll.firstNode)
print(list(ll)) # ['c']

node

• a node is just an instance of SimpleNamespace with three attributes
  • element: <can be anything>
  • next_: node
  • previous: node

print(ll.firstNode.element) # a
print(ll.firstNode.next_.element) # c
print(ll.lastNode.previous.element) # a
print(ll.firstNode.previous is None) # True

Test

#
# you must have poetry installed
#
$ poetry shell
$ poetry install
$ python runTests.py