I have created a python class for doubly linked list. It looks like this:
from tabulate import tabulate
class Node:
def __init__(self, value):
self.data = value
self.next = None # Next Node's address
self.prev = None # Previous Node's address
class DoublyLinkedList:
def __init__(self):
self.head = None # Empty linked list
self.tail = None # Last node in the list
self.n = 0 # Number of nodes
def __len__(self):
return self.n
def __str__(self):
curr = self.head
var = ''
while curr is not None:
var += ', '
var += str(curr.data)
curr = curr.next
return 'DLL [' + var[2:] + ']'
def print_structure(self):
curr = self.head
table = []
while curr is not None:
table.append([hex(id(curr.prev)) if not curr.prev is None else 'None, Head', curr.data,
hex(id(curr.next)) if not curr.next is None else 'None, Tail'])
curr = curr.next
print(tabulate(table, headers=['Prev Address', 'Data', 'Next Address'], tablefmt='psql'))
def insert_from_head(self, value):
new_node = Node(value)
new_node.next = self.head
if self.head is not None:
self.head.prev = new_node
self.head = new_node
if self.tail is None:
self.tail = new_node
self.n += 1
def append(self, value):
if self.head is None:
self.head = Node(value)
self.tail = self.head
else:
new_node = Node(value)
new_node.prev = self.tail
self.tail.next = new_node
self.tail = new_node
self.n += 1
def insert(self, index, value):
if self.head is None:
if index != 0:
raise IndexError('Linked List index out of range')
else:
self.head = Node(value)
self.tail = self.head
self.n += 1
else:
try:
new_node = Node(value)
curr = self.head
for i in range(index - 1):
curr = curr.next
new_node.next = curr.next
if curr.next is not None:
curr.next.prev = new_node
curr.next = new_node
new_node.prev = curr
if curr == self.tail:
self.tail = new_node
self.n += 1
except AttributeError:
raise IndexError('Linked List index out of range')
def clear(self):
self.head = None
self.tail = None
self.n = 0
def delete_head(self):
if self.head:
self.head = self.head.next
if self.head is not None:
self.head.prev = None
else:
self.tail = None
self.n -= 1
else:
raise IndexError('list assignment index out of range')
def pop(self):
if self.head is None:
raise IndexError('list assignment index out of range')
curr = self.head
if curr.next is None:
self.delete_head()
return
while curr.next.next is not None:
curr = curr.next
curr.next = None
self.tail = curr
self.n -= 1
def remove(self, value):
if self.head.data == value:
self.delete_head()
return
curr = self.head
while curr.next is not None:
if curr.next.data == value:
break
curr = curr.next
if curr.next is None:
raise ValueError(value + ' not in linked list')
curr.next = curr.next.next
if curr.next is not None:
curr.next.prev = curr
else:
self.tail = curr
self.n -= 1
def __delitem__(self, index):
if index == 0:
self.delete_head()
return
if index == self.n - 1:
self.pop()
return
curr = self.head
for i in range(index):
curr = curr.next
if curr is None:
raise IndexError('linked list assignment index out of range')
if curr.next is not None:
curr = curr.next
def __getitem__(self, index):
if not (0 <= index < self.n):
raise IndexError('list index out of range')
curr = self.head
for i in range(index):
curr = curr.next
return curr.data
def index(self, value):
curr = self.head
index = 0
while curr is not None:
if curr.data == value:
return index
curr = curr.next
index += 1
raise ValueError(f'{value} not in linked list')
def extend_array(self, array):
for i in array:
self.append(i)
I want to implement List Comprehensions and For In loops in this.
Lets say I have added these elements to the dll like this:
dll = DoublyLinkedList()
dll.extend_array([23, 41, 56, 85, 26, 63, 17, 2, 9, 8, 34, 238])
Now How do I make it so that these two pieces of code results in this output
for i in dll:
print(i, sep=', ')
OUTPUT:
23, 41, 56, 85, 26, 63, 17, 2, 9, 8, 34, 238
List Comprehension
arr = [i for i in dll]
print(arr)
OUTPUT:
[23, 41, 56, 85, 26, 63, 17, 2, 9, 8, 34, 238]
