Wrapping a class function by a decorator example.

gistfile1.py

class MyClass(object):

    def __repr__(self):
        return "<MyClass>"

    def my_hello(self):
        print "hello from", self


mc = MyClass()
mc.my_hello()  # prints "hello from <MyClass>"


def goodbye_func(self):
    print "goodbye from", self


def sayonara_func(self):
    print "sayanora from", self


# it's just a normal function that takes a parameter
goodbye_func(None)  # prints "goodbye from None"

# late assign a function to a class
MyClass.my_goodbye = goodbye_func

# still works on initialized classes
mc.my_goodbye()  # prints "goodbye from <MyClass>"


# now to wrap an object around a class

def wrap(cls):
    def wrapper(f):
        original_func = getattr(cls, f.__name__)

        def inner(self, *args, **kwargs):
            return f(self, original_func, *args, **kwargs)

        setattr(cls, f.__name__, inner)

    return wrapper


@wrap(MyClass)
def my_goodbye(self, func):
    print "enter from", self
    func(self)
    print "exit from", self


print mc.my_goodbye()  # prints "enter from <MyClass>, goodbye from <MyClass>, exit from <MyClass>"