Django - disable model editing

Question

Is there a way, hopefully without breaking admin, to disable editing existing model instances on the ORM level?

I'm not talking about removing 'Save' and 'Save and continue' buttons from templates - there should be no operations that can change the values of a committed instance of a model.

Preferably, the 'Save As' option should work instead.

Answer 1

Overwrite the save function for your model like so:

class MyModel(models.Model):

    def save(self, *args, **kwargs):

        if self.pk is None:
            super(MyModel, self).save(*args, **kwargs)

This function only call the superclass save function (which actually saves the change) if there is no pk, e.g. the model instance is new.