Leetcode 21 Merge Two Sorted Lists

Java:

class Solution {
public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
if(l1==null) return l2;
if(l2==null) return l1;
if(l1.val<l2.val){
l1.next=mergeTwoLists(l1.next,l2);
return l1;
}
else{
l2.next=mergeTwoLists(l1,l2.next);
return l2;
}
}
}

python3:
class Solution:
def mergeTwoLists(self, l1, l2):
"""
:type l1: ListNode
:type l2: ListNode
:rtype: ListNode
"""
if l1 and l2 :
if l1.val>l2.val:
l1,l2=l2,l1
l1.next=self.mergeTwoLists(l1.next,l2)
return l1 or l2;