[Django]-How to add a custom manager dynamically to model in django

You could write a factory function to create proxy models like this one:

def model_with_queryset(model_class, queryset_class):
    class Proxy(model_class):
        objects = queryset_class.as_manager()
        class Meta:
            proxy = True
            app_label = model_class._meta.app_label
    return Proxy

Here model_class would be any model you want to change the queryset on.

You could then create model classes dynamically:

SomeModelWithSomeQS = model_with_queryset(SomeModel, SomeQS)

and use them as any other (proxy) model.

The django-way would be to use the db.signals.class_prepared signal and draw inspiration from django.db.managers.ensure_default_manager() to properly add the manager to the class (mainly using model.add_to_class() to make sure the managers’s contribute_to_class() method is properly invoked). Then you’ll have to write some utility function to retrieve the appropriate queryset for a given model class.

Or you could write your own custom metaclass (based on django.db.models.base.ModelBase) and model class (using your custom metaclass) and make all your model classes inherit from it.

This being said, you’d really need to have a lot of models to even consider either of these solutions as economically valid…