How to declare abstract class and methods for model implementation?

Question

I wonder if there is a way in Django to create an abstract class where I can declare a method that should be implemented in a model.

Normally, in Python, we declare abstract class like this:

import abc

class MyABC(metaclass=abc.ABCMeta):

    @abc.abstractmethod
    def do_something(self, value):
        raise NotImplementedError

And then implement it like this:

class MyClass(MyABC):

    def do_something(self, value):
        pass

What I did with django is:

import abc
from django.db import models

class MyClass(metaclass=abc.ABCMeta):

    @abc.abstractmethod
    def __str__(self):
        raise NotImplementedError

class MyClass2(models.Model, MyClass):

    def __str__(self):
        pass

But this gives me error:

TypeError: metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases

I don't understand what I did wrong here. MyClass2 should inherit from MyClass and from models.Model.

What I did wrong? Why this is wrong? What is the better way of declaring methods that should be implemented in models?

Answer 1

For django model you can try this.

from django.db import models

class MyClass(models.Model):

   class Meta:
      abstract = True
   def __str__(self):
      raise NotImplementedError

class MyClass2(MyClass):

   def __str__(self):
       pass

refer this hope this helps.