import time

def performance(f):

    def fn(*args,**kw):

        t1 = time.time()

        r = f(*args, **kw)

        t2 = time.time()

        print 'call %s() in %fs' % (f.__name__, (t2 - t1))

        return r

    return fn

@performance

def factorial(n):

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

print factorial(10)