Give a Python class a brain transplant by modifying __class___.

brain_transplant.py

class Foo(object):
  def whoami(self):
    self.foowuz = 666
    print("I'm Foo, foo!")

class Bar(object):
  def whoami(self):
    self.barwuz = 777
    print("I'm Bar, sucka!")

obj = Foo()
obj.whoami()
# prints I'm Foo, foo!
# foowuz = 666
# no attribute barwuz

obj.__class__ = Bar
obj.whoami()
# prints I'm Bar, sucka!
# foowuz = 666
# barwuz = 777