delegator.py

classDelegator:

def__init__(self, delegate=None):
self.delegate=delegate
self.__cache=set()
# Cache is used to only remove added attributes
# when changing the delegate.

def__getattr__(self, name):
attr=getattr(self.delegate, name) # May raise AttributeError
setattr(self, name, attr)
self.__cache.add(name)
returnattr

defresetcache(self):
"Removes added attributes while leaving original attributes."
# Function is really about resetting delegator dict
# to original state. Cache is just a means
forkeyinself.__cache:
try:
delattr(self, key)
exceptAttributeError:
pass
self.__cache.clear()

defsetdelegate(self, delegate):
"Reset attributes and change delegate."
self.resetcache()
self.delegate=delegate


if__name__=='__main__':
fromunittestimportmain
main('idlelib.idle_test.test_delegator', verbosity=2)