Merge two Sorted Linked List hacker rank solution python

 #!/bin/python3

import math

import os

import random

import re

import sys

class SinglyLinkedListNode:

    def __init__(self, node_data):

        self.data = node_data

        self.next = None

class SinglyLinkedList:

    def __init__(self):

        self.head = None

        self.tail = None

    def insert_node(self, node_data):

        node = SinglyLinkedListNode(node_data)

        if not self.head:

            self.head = node

        else:

            self.tail.next = node

        self.tail = node

def print_singly_linked_list(node, sep, fptr):

    while node:

        fptr.write(str(node.data))

        node = node.next

        if node:

            fptr.write(sep)

# Complete the mergeLists function below.

#

# For your reference:

#

# SinglyLinkedListNode:

#     int data

#     SinglyLinkedListNode next

#

#

def mergeLists(head1, head2):

    dummy=SinglyLinkedListNode(None) #create a dummy node

    tail=dummy

    while head1 and head2:

        if head1.data<head2.data:

            tail.next=head1

            head1=head1.next

        else:

            tail.next=head2

            head2=head2.next

        tail=tail.next

    if head1:

        tail.next=head1

    else:

        tail.next=head2

    return dummy.next 

if __name__ == '__main__':