member_decorator.py

class Implementation(object):
    def __init__(self, func, x):
        self.func = func
        self.x = x

    def __call__(self, *args, **kwargs):
        return self.decorator(*args, **kwargs)

    def decorator(self, *args, **kwargs):
        y = 10
        print "x + {0} = {1}".format(y, self.x + y)
        return self.func(*args, **kwargs)


class DescriptorDecorator(object):
    def __init__(self, klass, x=None):
        self.klass = klass
        self.x = x

    def __call__(self, func):
        self.func = func
        return self

    def __get__(self, obj, type=None):
        # Reflect bound method to wrapped class method
        return self.klass(self.func.__get__(obj, type), x=self.x)


def my_decorator(x=None):
    return DescriptorDecorator(Implementation, x=x)


class SomeClass(object):
    @my_decorator(x=5)
    def foo(self):
        print 'Foo'

if __name__ == '__main__':
    instance = SomeClass()
    print instance.foo
    instance.foo()