Another question about these PluggableBrains I'm developing for my application. I haven't been able to find much definitive, complete documentation on the subject anywhere. So I'm pretty much figuring it out by trial-and error. My class has an __init__ method like so: def __init__(self): "Initialize class" self._badmsgs = {} # function: reason # Validation info... self._invalidated = False # Have we been specifically invalidated by a set function? self._valid = True # Are we valid? When I access a query using this Brains class, I get an AttributeError complaining about _badmsgs. What is causing this? It occurs even if I declare _badmsgs = {} outside the __init__ function.