add two numbers || linked list python leetcode solution

 # class ListNode:

#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def addTwoNumbers(self, l1: Optional[ListNode], l2: Optional[ListNode]) -> Optional[ListNode]:
        dummy=ListNode(None)
        tail=dummy
        carry=0
        while l1 or l2 or carry:
            v1=l1.val if l1 else 0  # there might be a case where 2 digit
            v2=l2.val if l2 else 0   # number is add with 3 so we add 0
            """1-->2-->9
                2-->3-->2-->1 in above we place 0 """
            val=v1+v2+carry
            carry=val//10 # it stores 10th place in carry 
            val=val%10
            tail.next=ListNode(val)
            l1=l1.next if l1 else None
            l2=l2.next if l2 else None
            tail=tail.next
        return dummy.next