Monkey patching a @property

Question

Is it at all possible to monkey patch the value of a @property of an instance of a class that I do not control?

class Foo:     @property     def bar(self):         return here().be['dragons']  f = Foo() print(f.bar)  # baz f.bar = 42    # MAGIC! print(f.bar)  # 42 

Obviously the above would produce an error when trying to assign to f.bar. Is # MAGIC! possible in any way? The implementation details of the @property are a black box and not indirectly monkey-patchable. The entire method call needs to be replaced. It needs to affect a single instance only (class-level patching is okay if inevitable, but the changed behaviour must only selectively affect a given instance, not all instances of that class).

Answer 1

Subclass the base class (Foo) and change single instance's class to match the new subclass using __class__ attribute:

>>> class Foo: ...     @property ...     def bar(self): ...         return 'Foo.bar' ... >>> f = Foo() >>> f.bar 'Foo.bar' >>> class _SubFoo(Foo): ...     bar = 0 ... >>> f.__class__ = _SubFoo >>> f.bar 0 >>> f.bar = 42 >>> f.bar 42