Overriding __getattribute__ for the Model class in Django

In Django, I need to create a model in which an instance of that model can inherit values from another instance of that model in what amounts to a superclass-subclass type relationship. I created a field in this model called parent, which is an optional self-referencing foreign key. I then want to override the __getattribute__ method as follows:

def __getattribute__(self, name):
    if models.Model.__getattribute__(self, 'parent') is None:
        return models.Model.__getattribute__(self, name)
    elif models.Model.__getattribute__(self, name) is not None:
        return models.Model.__getattribute__(self, name)
 开发者_StackOverflow   else:
        return parent.__getattribute__(name)

This code causes an infinite recursion because the __get__ method of the Model class calls the built-in method getattr passing in the instance as the first parameter.

Is there another way to accomplish what I'm trying to do?

This is fraught with difficulty when done this way.

Please reconsider overriding __getattribute__ and use a plain old properties for this.

I suspect that a simple "getter" with a property names will do eveything you want without bumping into any magic.

Yes, you may have several similar fields, but I think that simple, obvious properties fit better with the Django ORM.

Do you need that parent's attributes shadow own ones? If not, you'd better overwrite __getattr__() instead of __getattribute__() which is not called when instance itself has property with this name:

def __getattr__(self, name):
    return getattr(self.parent, name)

I suppose that overriding __getattribute__ or __getattr__ may lead to performance cost. Probably there is a better way to solve this problem:

1. On model instance initialization, if an inheritable field is empty and corresponding parent's field is not, do setattr(self, field_name, getattr(self.parent, field_name)).
2. Keep track of model instance field changes.
3. Before saving the instance, set the fields that were previously overridden but not changed to None.

I'm developing a Django app for that: https://github.com/Altaisoft/django-inheritance