Iterating over object instances of a given class in Python

Question

Given a class that keeps a registry of its Objects:

class Person(object):
   __registry = []

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


        

Answer 1

You can make your class object iterable with a simple metaclass.

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

(I have also changed __registry to _registry to make it easier to access from the metaclass). Then,

>>> p = Person('John')
>>> p2 = Person('Mary')
>>> for personobject in Person:
...     print personobject
...