Django Singleton Model and ModelAdmin

signleton_model.py

from django.db import models
from django.contrib import admin
from django.contrib.admin.options import csrf_protect_m


class SingletonModel(models.Model):

    class Meta:
        abstract = True

    def save(self, *args, **kwargs):
        self.pk = 1
        super().save(*args, **kwargs)

    def delete(self, *args, **kwargs):
        pass  # or return some reasonable validation/permission error.

    @classmethod
    def load(cls):
        try:
            return cls.objects.get(pk=1)
        except cls.DoesNotExist:
            raise Exception('You have to create "{}" first.'.format(cls.__name__))


class SingletonModelAdmin(admin.ModelAdmin):
    """
    Class for SingletonModel subclasses to skip change list view and
    hide "Add" and "Save and add another" buttons is instance already exists.
    """

    @csrf_protect_m
    def changelist_view(self, request, extra_context=None):
        instance = self.model.objects.first()
        return self.changeform_view(
                request=request,
                object_id=str(instance.id) if instance else None,
                extra_context=extra_context)

    def has_add_permission(self, request):
        return not self.model.objects.exists()