jpayne@68: class Delegator:
jpayne@68: 
jpayne@68:     def __init__(self, delegate=None):
jpayne@68:         self.delegate = delegate
jpayne@68:         self.__cache = set()
jpayne@68:         # Cache is used to only remove added attributes
jpayne@68:         # when changing the delegate.
jpayne@68: 
jpayne@68:     def __getattr__(self, name):
jpayne@68:         attr = getattr(self.delegate, name) # May raise AttributeError
jpayne@68:         setattr(self, name, attr)
jpayne@68:         self.__cache.add(name)
jpayne@68:         return attr
jpayne@68: 
jpayne@68:     def resetcache(self):
jpayne@68:         "Removes added attributes while leaving original attributes."
jpayne@68:         # Function is really about resetting delegator dict
jpayne@68:         # to original state.  Cache is just a means
jpayne@68:         for key in self.__cache:
jpayne@68:             try:
jpayne@68:                 delattr(self, key)
jpayne@68:             except AttributeError:
jpayne@68:                 pass
jpayne@68:         self.__cache.clear()
jpayne@68: 
jpayne@68:     def setdelegate(self, delegate):
jpayne@68:         "Reset attributes and change delegate."
jpayne@68:         self.resetcache()
jpayne@68:         self.delegate = delegate
jpayne@68: 
jpayne@68: if __name__ == '__main__':
jpayne@68:     from unittest import main
jpayne@68:     main('idlelib.idle_test.test_delegator', verbosity=2)