Tip

Pretty Poor Polymorphism

There's a fine line between flexibility and foolishness.

We may have stepped over the edge off flexible into foolish as soon as we feel the need to write:

if 'x' in self.__dict__:

Or:

try:
    self.x
except AttributeError:

It's time to reconsider the API and add a common method or attribute. Refactoring is better than adding if statements.