Rewriting __getattr__

[kost BebiX]

Hi everyone!
I just saw a bug (?) in bson.dbref:DBRef.__getattr__

Here's they're code:
    def __getattr__(self, key):
        return self.__kwargs[key]

And when you do copy.deepcopy on that object it will raise you KeyError. So here's a small piece of code that reproduces the problem:

>>> class A(object):
..     def __init__(self):
..         self.d = {}
..     def __getattr__(self, key):
..         self.d[key]
.. a = A()
.. copy.deepcopy(a)
Traceback (most recent call last):
  File "<pyshell#17>", line 7, in <module>
    copy.deepcopy(a)
  File "/usr/lib/python2.6/copy.py", line 171, in deepcopy
    copier = getattr(x, "__deepcopy__", None)
  File "<pyshell#17>", line 5, in __getattr__
    self.d[key]
KeyError: '__deepcopy__'

So I thought the right thing right now will be to do just:

class A(object):
    def __init__(self):
        self.d = {}
    def __getattr__(self, key):
        if key.startswith('__'):
            raise AttributeError
        self.d[key]

and it works, but... isn't that wrong? I mean, shouldn't deepcopy somehow work in this situation, or, maybe, something else should differ? And why this code:

class A(object):
    def __init__(self):
        self.d = {}
    def __getattr__(self, key):
        if key in dir(self.d):
            return self.d[key]
        raise AttributeError
a = A()
deepcopy(a)

gets "maximum recursion depth exceeded"?

Thank you.

-- 
jabber: kost-bebix at ya.ru