Leetcode (Python): Merge Two Sorted Lists

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

Solution:

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

class Solution:
    # @param two ListNodes
    # @return a ListNode
    def mergeTwoLists(self, l1, l2):
        dummy = ListNode(0)
        pointer = dummy
        while l1 !=None and l2 !=None:
            if l1.val<l2.val:
                pointer.next = l1
                l1 = l1.next
            else:
                pointer.next = l2
                l2 = l2.next
            pointer = pointer.next
        if l1 == None:
            pointer.next = l2
        else:
            pointer.next = l1
        return dummy.next