class Person(object):
   __registry = []

   def __init__(self, name):
       self.__registry.append(self)
       self.name = name

for personobject in Person:
    print personobject

class IterRegistry(type):
    def __iter__(cls):
        return iter(cls._registry)

class Person(object):
    __metaclass__ = IterRegistry
    _registry = []

    def __init__(self, name):
        self._registry.append(self)
        self.name = name

>>> p = Person('John')
>>> p2 = Person('Mary')
>>> for personobject in Person:
...     print personobject
...
<person.Person object at 0x70410>
<person.Person object at 0x70250>

class Person(object):
    _registry = []

    def __init__(self, name):
        self._registry.append(self)
        self.name = name

for p in Person._registry:
    print p

for item in Person.__registry:
    print(item)