how to have "city" fields depending on "country" field in Django models, without creating their tables

I know there are several questions asked like this (such as this one), but non of them could help me with my problem.

I wanna have a City and a Country field in my models, which the City choices is depended on Country; BUT I do not want to define City and Country as models classes. here is my code :

from django.contrib.auth.models import User
from django.db import models
from django.forms import ChoiceField
from django_countries.fields import CountryField


class UserProfile(models.Model):
    user = models.OneToOneField(User, related_name="UserProfile")
    name = models.CharField(max_length=30, null=False, blank=False)
    picture = models.ImageField(upload_to='userProfiles/', null=False, blank=False)
    date_of_birth = models.DateTimeField(null=False, blank=False)
    country = CountryField()
    # city = ??
    national_code = models.IntegerField(max_length=10, null=False, blank=False)
    email = models.EmailField()

    def __str__(self):
        return '{}'.format(self.user.username)

    def __unicode__(self):
        return self.user.username

just like field "country" which is country = CountryField(), I wonder if there is a way that I could do the mission without defining the class Country(models.Model) or class City(models.Model)

In order to do this you can use django-cities.

However, this will not resolve the issue with the input logic - if you need something like filtering the cities after selecting a country in your forms. You could use django-smart-selects for this but I am not sure how easy it is to implement the complex model structure of django-cities.