python - Function that iterates through a linked list -

class ln:     def __init__(self,value,next=none):         self.value = value         self.next  = next  def list_to_ll(l):     if l == []:         return none     front = rear = ln(l[0])     v in l[1:]:         rear.next = ln(v)         rear = rear.next     return front  def add_after(ll,value,new):     item in ll:         if item == value:             ll.insert(ll.index(value),new) 

i working on iterative function named add_after. takes linked list , 2 values, value , new. mutates linked list such every occurrence of value followed new. example:

a = list_to_ll([2,1,8,2,2,4,2,5,2]) 

add_after(a,2,-1) results in referring linked list containing values 1->8->2->-1->4->2->-1->5->2->-1->none.

add_after(a,2,2) original list in results in referring linked list containing values 1->8->2->2->4->2->2->5->2->2->none.

plus( not allowed use lists, tuples, sets, or dicts in code)

use linked lists processing only

when run add_after gives me error:

add_after(ll,2,-1) item in ll: typeerror: 'ln' object not iterable 

can me fix add_after function? many thanks.

1. make ln iterable, defining __iter__ methods yields nodes:
2. make add_after link new node.

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class ln:     def __init__(self, value, next=none):         self.value = value         self.next  = next      def __iter__(self):  # yield linked node (including first node)         node = self         while node not none:             yield node             node = node.next  def list_to_ll(l):     if l == []:         return none     front = rear = ln(l[0])     v in l[1:]:         rear.next = ln(v)         rear = rear.next     return front  def add_after(ll, value, new):     item in ll:         if item.value == value:             ll.next = ln(new, ll.next)  # make new node , link after current node             break     # todo: handle not-found case.   ll = list_to_ll([2,1,8,2,2,4,2,5,2]) add_after(ll, 2, -1) item in ll:     print(item.value)  # prints 2, -1, 1, 8, 2, 2, 4, 2, 5, 2 

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update after reading op's comment => changing add_after (manually loop through nodes):

def add_after(ll, value, new):     node = ll     while node not none:         if node.value == value:             node.next = ln(new, node.next)             break         node = node.next 

note: made add_after add 1 node. leave work add multiple nodes.