gistfile1.py

# I have (models.py)
from django.db import models

class ParentModel(models.Model):
    field_a = ...
    field_b = ...
    
    def a_method(self):
        pass


class ChildModelA(ParentModel):
    field_c = ...
    
    def a_method(self):
        print "A"

    def b_method(self):
        print self.field_c


class ChildModelB(ParentModel):
    field_d = ....

    def a_method(self):
        print "B"

    def b_method(self):
        print self.field_d


# What I'd like to do:

>>> obj = ParentModel.objects.get(pk=n) # Same thing with filter as well
>>> obj.a_method()
# If it happens that obj is a ChildA instance:
"A"
# If it's a ChildB instance:
"B"
>>> obj.b_method()
# The correct result here according to obj's class.