>>> class mydict(dict):
...     def __getitem__(self, key):
...         return 17
...
>>> class blah(object):
...     def __init__(self):
...         self.__dict__ = mydict()
...
>>> b = blah()
>>> print b.x
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
AttributeError: 'blah' object has no attribute 'x'

python doesn't call the overriden version of __getitem__.  

i've done several more tests, and the cause to this
problem, afaik, is that the code assumes __dict__ is an
instance of dict, so it directly uses PyDict_GetItem
(or whatever it's called), thus skipping the overriden
method.

python should either disable setting __dict__ to
anything that is not a real dict (type(x) == dict
instead of isinstance(x, dict)), or be willing to call
overriden methods.

Confirmed, is this a valid issue?

2.5 and 2.4 are in security-fix-only mode, so we don't set them in
versions since bugs won't get fixed there.

I don't think overridden methods should be called, since that would slow
down attribute lookup, which is already a bottleneck in Python.  Whether
there should be an error message is a more complicated question, and I'd
have to look at how this is implemented to even have an opinion on that.