def logger(func):
    def new_func(*args, **kwds):
        try:
            print 'enter %s' % func.func_name
            return func(*args, **kwds)
        finally:
            print 'exit %s' % func.func_name
    return new_func

def add(a, b): return a+b
add = logger(add)
print add(20, 22)