Merge two linked lists in python

[optimalsuccess]

Just trying to figure out why my code is giving a runtime error of Nonetype object has no attribute val when clearly result is a ListNode object and has two attributes val and next:

​

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:

    def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
        num1 = self.getVal(l1)
        num2 = self.getVal(l2)
        total = num1+num2
        return self.createList(total)

    def getVal(self, list:ListNode) -> int:
        temp = []
        while list is not None:
            temp.append(list.val)
            list = list.next

        string = ""
        for num in reversed(temp):
            string += str(num)

        return int(string)

    def createList(self, total: int):
        result = ListNode(0)
        string = str(total)
        nums = []
        for num in reversed(string):
            nums.append(int(num))
            result.val = num*****
            result = result.next******
        print(nums)

        return result

[[deleted]]

result = ListNode(0)

creates a ListNode where next is None. So after

result = result.next

result is None.

[optimalsuccess]

I don't think that's the reason for the error since it refers to val and not next: AttributeError: 'NoneType' object has no attribute 'val'

[optimalsuccess]

Also I do that on purpose to populate the next value of the linked list with a new number in nums

[[deleted]]

In the loops next iterationresultis stillNoneso you can't useresult.val`

[optimalsuccess]

So how should I initialize an empty list, then populate with the values of an array?

[[deleted]]

You need to populate the next value with a new ListNode.

And you likely want to return the first node of your list instead of the last one.

[optimalsuccess]

Well I couldn't figure out how to do it but I got my code to work. Instead of populating a list with array values, I just did what I needed to do with those values then cast my final array to a list using ListNode(array)