import time, functools

def performance(unit):

    def perf_decorator(f):

        def wrapper(*args, **kw):

            t1 = time.time()

            r = f(*args, **kw)

            t2 = time.time()

            t = (t2 - t1) * 1000 if unit=='ms' else (t2 - t1)

            print 'call %s() in %f %s' % (f.__name__, t, unit)

            return r

        return wrapper

    return perf_decorator

@performance('ms')

def factorial(n):

    return reduce(lambda x,y: x*y, range(1, n+1))

print factorial.__name__