def metric(fn):

@functools.wraps(fn)

def wrapper(*args, **kw):

    start_time = time.time()
    fn(*args, **kw) #写成x = fn(XXXX)和不写 x =好像都可以
    end_time = time.time()

    print('%s executed in %s ms' % (fn.__name__, 1000 * (end_time - start_time)))

    return fn(*args, **kw)

return wrapper