jpayne@69: class Delegator:
jpayne@69: 
jpayne@69:     def __init__(self, delegate=None):
jpayne@69:         self.delegate = delegate
jpayne@69:         self.__cache = set()
jpayne@69:         # Cache is used to only remove added attributes
jpayne@69:         # when changing the delegate.
jpayne@69: 
jpayne@69:     def __getattr__(self, name):
jpayne@69:         attr = getattr(self.delegate, name) # May raise AttributeError
jpayne@69:         setattr(self, name, attr)
jpayne@69:         self.__cache.add(name)
jpayne@69:         return attr
jpayne@69: 
jpayne@69:     def resetcache(self):
jpayne@69:         "Removes added attributes while leaving original attributes."
jpayne@69:         # Function is really about resetting delegator dict
jpayne@69:         # to original state.  Cache is just a means
jpayne@69:         for key in self.__cache:
jpayne@69:             try:
jpayne@69:                 delattr(self, key)
jpayne@69:             except AttributeError:
jpayne@69:                 pass
jpayne@69:         self.__cache.clear()
jpayne@69: 
jpayne@69:     def setdelegate(self, delegate):
jpayne@69:         "Reset attributes and change delegate."
jpayne@69:         self.resetcache()
jpayne@69:         self.delegate = delegate
jpayne@69: 
jpayne@69: if __name__ == '__main__':
jpayne@69:     from unittest import main
jpayne@69:     main('idlelib.idle_test.test_delegator', verbosity=2)