PyCon

meta.py

from trace import traced

class Tracer(type):
    def __new__(cls, name, bases, cdict):
        for n in cdict:
            if callable(cdict[n]) \
                and not n.startswith("__"):
                cdict[n] = traced(cdict[n])
        return type.__new__(cls, name, bases, cdict)

if __name__ == "__main__":
    class MyClass(object):
        __metaclass__ = Tracer
        def method1(self, a):
            print "Method 1:", a
        def method2(self, a, b=10):
            return "Method 2: %s" % (a*b)

    mc = MyClass()
    mc.method1("Hooray!")
    print mc.method2("Easy", b=3)

trace.py

def traced(f):
    def tracer(*args, **kw):
        print ("** %s(%s)") % (
                f.__name__,
                ", ".join(
                     [repr(arg) for arg in args]+
                     ["%s=%s" % (k, repr(v))
                         for (k, v) in kw.items()]))
        return f(*args, **kw)
    return tracer