django_singleton.py

from django.db import models
from django.contrib import admin
from django.shortcuts import redirect


class SingletonModel(models.Model):
    class Meta:
        abstract = True

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


class SingletonModelAdmin(admin.ModelAdmin):
    actions = None

    def has_delete_permission(self, request, obj=None):
        return False

    def changelist_view(self, request, *args, **kwargs):
        app_label, model_name = (
            self.model._meta.app_label,
            self.model._meta.model_name,
        )
        try:
            singleton = self.get_queryset(request).get()
        except self.model.MultipleObjectsReturned:
            return super().changelist_view(request, *args, **kwargs)
        except self.model.DoesNotExist:
            return redirect(f"admin:{app_label}_{model_name}_add")
        return redirect(f"admin:{app_label}_{model_name}_change", singleton.id)


class SingletonInlineMixin:
    max_num = 1
    min_num = 1

    def has_delete_permission(self, request, obj=None):
        return False