trapping all method calls in a class...

Chris Rebert clp at
Sun Dec 21 08:32:14 CET 2008

On Sat, Dec 20, 2008 at 11:12 PM, Piyush Anonymous
<piyush.subscription at> wrote:
> hi,
> i need to trap all method calls in a class in order to update a counter
> which is increased whenever a method is called and decreased whenever method
> returns. in order to that i am trying to write a decorator for all the
> methods.
> see the code here with error.
> -------
> ----
> any suggestions? any other better way of doing it?

I call unnecessary use of metaclasses! Here's my (untested) attempt at
a simpler class decorator approach:

def decorate_meths(klass):
    attrs = klass.__dict__.items()
	for name, val in attrs:
		if callable(val):
			klass.__dict__[name] = decorate(val)

def decorate(method):
    #should be called for every method call in the class
    def decorated(self, *args, **kwds):
        print "2 Inside __call__()"
        returnval = method(self, *args,**kwds)
        print "3 After self.f(*args)"
        return returnval
    return decorated

#@decorate_meths <-- this syntax requires a later Python version
class Person(object):
	def testprint(self,val):
		print "blah blah"
Person = decorate_meths(Person)

#rest of code after the class definition would be the same

Sidenotes about your code:
- `args` and `kwds` are the conventional names for the * and **
special arguments
- the `methodname` variable was actually getting method objects, not
strings, as its values; this was probably part of the bug in your


Follow the path of the Iguana...

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