Metaclass to bake hybrid class/instance binding decorators into subclasses

bindings.py

def bind(clsname, first, second=None):
    if second is None:  # class binding
        cls = globals()[clsname]
        fn = first
        name = fn.fget.__name__ if isinstance(fn, property) else fn.__name__
        setattr(cls, name, fn)
    else:  # instance binding
        self = first
        fn = second
        name = fn.fget.__name__ if isinstance(fn, property) else fn.__name__
        setattr(self, name, partial(fn, self))

class BindableMeta(type):
    def __new__(cls, name, bases, dct):
        def inner(*args):
            return bind(name, *args)
        dct["bind"] = inner
        return type.__new__(cls, name, bases, dct)


class Bindable(metaclass=BindableMeta):
    pass
  
# Examples:

class Foo(Bindable):
    pass

@Foo.bind
def bar(self):
    return 5

f = Foo()
assert f.bar() == 5

@f.bind
def bat(self):
    return 5

assert f.bat() == 5
g = Foo()
try:
    assert g.bat() == 5
except AttributeError:
    pass
else:
    raise RuntimeError("shouldn't work")

@Foo.bind
@property
def prop(self):
    return 5

assert f.prop == 5