merge_linked_list.py

def mergeLists(head1, head2):
    llist3 = SinglyLinkedList()
    while head1 or head2:
        if head1 == None:
            llist3.insert_node(head2.data)
            head2 = head2.next
        elif head2 == None:
            llist3.insert_node(head1.data)
            head1 = head1.next
        elif head1.data >= head2.data:
            llist3.insert_node(head2.data)
            head2 = head2.next
        elif head2.data > head1.data:
            llist3.insert_node(head1.data)
            head1 = head1.next
    return llist3.head