Python Class Based Decorator with parameters that can decorate a method or a function

Question

I\'ve seen many examples of Python decorators that are:

• function style decorators (wrapping a function)
• class style decorators (implementing __i

Answer 1

In your list of types of decorators, you missed decorators that may or may not take arguments. I think this example covers all your types except "function style decorators (wrapping a function)"

class MyDecorator(object):

    def __init__(self, argument):
        if hasattr('argument', '__call__'):
            self.fn = argument
            self.argument = 'default foo baby'
        else:
            self.argument = argument

    def __get__(self, obj, type=None):
        return functools.partial(self, obj)

    def __call__(self, *args, **kwargs):
        if not hasattr(self, 'fn'):
            self.fn = args[0]
            return self
        print "In my decorator before call, with arg %s" % self.argument
        self.fn(*args, **kwargs)
        print "In my decorator after call, with arg %s" % self.argument


class Foo(object):
    @MyDecorator("foo baby!")
    def bar(self):
        print "in bar!"

class Bar(object):
    @MyDecorator
    def bar(self):
        print "in bar!"

@MyDecorator
def add(a, b):
    print a + b