when I try add before(use method:-> add_before() <-) element he give me a error
this error 
go to last code I add some comment 
#todo: create Linked List:
class Node:
def __init__(self, data):
self.data = data
self.next = None
def __repr__(self):
return self.data
class LinkedList:
def __init__(self, nodes=None):
self.head = None
#-: make linked list much faster
if nodes is not None:
node = Node(data=nodes.pop(0))
self.head = node
for elem in nodes:
node.next = Node(data=elem)
node = node.next
#-: Return a string
def __repr__(self):
node = self.head
nodes = []
while node is not None:
nodes.append(node.data)
node = node.next
nodes.append('None')
return ' ->'.join(nodes)
#-: to loop to all list if you add all list at one
def __iter__(self):
node = self.head
while node is not None:
yield node
node = node.next
#-: add new node to the head
def add_first(self, node):
node.next = self.head
self.head = node
#-: add the new node to the last
def add_last(self, node):
if self.head is None:
self.head = node
return
for current_node in self:
pass
current_node = node
#-: adds a node afer an existing node with specific data value
def add_after(self, target_node_data, new_node):
if self.head is None:
raise Exception('List is empty')
for node in self:
if node.data == target_node_data:
new_node.next = node.next
node.next = new_node
return
raise Exception("Node with data '%s' not found "% target_node_data)
#-: add before existing node
def add_before(self, target_node_data, new_node):
if self.head is None:
raise Exception('List is empty')
#: add node before the head
if self.head.data == target_node_data:
return self.add_first(new_node)
# in example -> prev_node = b
#prev_node.next = c
#target_node_data = G
prev_node = self.head
for node in self:
if node.data == target_node_data:
# here I make prev_node.next = G
prev_node.next = new_node
#here is the error , I want make (G) to point to (c)
new_node.next = node
return
prev_node = node
raise Exception("Node With data '%s' not found"% target_node_data)
