Question

I don’t know why this doesn’t work:

I’m using the odict class from PEP 372, but I want to use it as a __dict__ member, i.e.:

class Bag(object):     def __init__(self):         self.__dict__ = odict() 

But for some reason I’m getting weird results. This works:

>>> b = Bag() >>> b.apple = 1 >>> b.apple 1 >>> b.banana = 2 >>> b.banana 2 

But trying to access the actual dictionary doesn’t work:

>>> b.__dict__.items() [] >>> b.__dict__ odict.odict([]) 

And it gets weirder:

>>> b.__dict__['tomato'] = 3 >>> b.tomato 3 >>> b.__dict__ odict.odict([('tomato', 3)]) 

I’m feeling very stupid. Can you help me out?

Answer 1

The closest answer to your question that I can find is at http://mail.python.org/pipermail/python-bugs-list/2006-April/033155.html.

Basically, if __dict__ is not an actual dict(), then it is ignored, and attribute lookup fails.

The alternative for this is to use the odict as a member, and override the getitem and setitem methods accordingly.

>>> class A(object) : ...     def __init__(self) : ...             self.__dict__['_odict'] = odict() ...     def __getattr__(self, value) : ...             return self.__dict__['_odict'][value] ...     def __setattr__(self, key, value) : ...             self.__dict__['_odict'][key] = value ...  >>> a = A() >>> a <__main__.A object at 0xb7bce34c> >>> a.x = 1 >>> a.x 1 >>> a.y = 2 >>> a.y 2 >>> a.odict odict.odict([('x', 1), ('y', 2)])