Add Two Numbers.py

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

class Solution(object):
    def addTwoNumbers(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """

        resultlist = ListNode(0)
        current = resultlist
        carry = 0

        while l1 or l2 or carry:
            val1 = l1.val if l1 is not None else 0
            val2 = l2.val if l2 is not None else 0
            result = val1 + val2 + carry
            carry = result // 10
            current.next = ListNode(result % 10)
            current = current.next

            if l1:
                l1 = l1.next
            if l2:
                l2 = l2.next

        return resultlist.next