Django User model one time pin code OTP

user_model_with_otp.py

import hashlib
from django.db import models
from django.contrib.auth.models import AbstractUser

class User(AbstractUser):
    created_at = models.DateTimeField(auto_now_add=True)

    def get_otp(self, num_digits=4):
        """
        generate random pin code 
        this will return the same value until the next time the user logs in
        therefore, it can be called in view logic to both create and validate the code before login
        """
        hash_object = hashlib.md5(bytes(f"{self.username}{self.created_at}{self.last_login}", encoding='utf-8'))
        return str(int(hash_object.hexdigest(), 16))[-num_digits:]