def metric(fn):
    @functools.wraps(fn)
    def wrapper(*args, **kwargs):
        t1 = time.time()
        res = fn(*args, **kwargs)
        print('%s executed in %s ms' % (fn.__name__, (time.time() - t1)*1000))
        return res
    return wrapper

print 这里单位是ms， time.time() 和  time.sleep(0.0012)的单位都是秒