Enforced abstract base classes

gistfile1.py

class AbstractBaseMetaClass(type):
    def __new__(meta, classname, bases, attributes):
        if getattr(meta, '_required_methods', None) is None:
            meta._required_methods = []

            for name, attribute in attributes.items():
                if name == '__metaclass__':
                    continue
                if callable(attribute):
                    meta._required_methods.append(name)
        else:
            for required_method in meta._required_methods:
                if required_method not in attributes:
                    raise Exception('OMG')

        return type.__new__(meta, classname, bases, attributes)

class AbstractBaseClass(object):
    __metaclass__ = AbstractBaseMetaClass

    def required_method(self):
        pass

class CorrectClass(AbstractBaseClass):
    def required_method(self):
        pass

class IncorrectClass(AbstractBaseClass):
    def optional_method(self):
        pass