Leetcode: Add Two Numbers @Python

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

class Solution:
    # @return a ListNode
    def addTwoNumbers(self, l1, l2):
        num1,num2=0,0
        digit=0
        while l1:
            num1+=l1.val*(10**digit)
            l1=l1.next
            digit+=1
        digit=0
        while l2:
            num2+=l2.val*(10**digit)
            l2=l2.next
            digit+=1
        numsum=num1+num2
        numsum,val=divmod(numsum,10)
        keephead=head=ListNode(val)
        while numsum:
            numsum,val=divmod(numsum,10)
            crt=ListNode(val)
            head.next=crt
            head=crt
        return keephead