mixin helper class for unknown attribute access?

[Alex Hunsley]

I know that I can catch access to unknown attributes with code something 
like the following:

class example:
      def __getattr__(self, name):
          if name == 'age':
              return __age
          else:
              raise AttributeError


but is there an existing mixin helper class in Python (or one someone 
has written) already that will assist with this? (Just not wanting to 
reinvent the wheel....)