Sample Interface implementation in python

abc_interface_models.py

"""
This is my interface functionality implementation using abc
"""
import abc
from django.db import models
from django.contrib.contenttypes.models import ContentType
from django.contrib.contenttypes.generic import GenericForeignKey


class AbstractBase():
    """
    Abstract class that used as interface
    This class makes sure that child classes have
    my_method implemented
    """
    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod
    def my_method(self):
        return


class MyModel(models.Model):

    def my_method(self):
        return 1

AbstractBase.register(MyModel)


class MyOtherModel(models.Model):

    def my_method(self):
        return 2

AbstractBase.register(MyOtherModel)


class MyModelConsumer(models.Model):
    """
    This object uses content_object generic foreign key in
    its algorithms. There should be a better way of 
    """
    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField()
    content_object = GenericForeignKey()

    def use_object(self):
        self.content_object.my_method()

    def assign_object(self, obj):
        "object must inherit Abstract Base"
        self.content_object = obj

zope_interface_models.py

"""
Sample interface using zope.interface
(Does not do any validation at all)
"""
from django.db import models
from django.contrib.contenttypes.models import ContentType
from django.contrib.contenttypes.generic import GenericForeignKey
from zope import interface


class IBase(interface.Interface):
    """
    This class makes sure that child classes have
    my_method implemented
    """

    def my_method(self):
        return


class MyModel(models.Model):
    interface.implements(IBase)

    def _my_method(self):
        return 1


class MyOtherModel(models.Model):
    interface.implements(IBase)

    def my_method(self):
        return 2


class MyModelConsumer(models.Model):
    """
    This object uses content_object generic foreign key in
    its algorithms. There should be a better way of
    """
    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField()
    content_object = GenericForeignKey()

    def use_object(self):
        self.content_object.my_method()

    def assign_object(self, obj):
        assert IBase.provided_by(obj)
        "object must inherit Abstract Base"
        self.content_object = obj