def metric(fn):

@functools.wraps(fn)
def wrapper(*args, **kw):
    start = time.time()
    fn(*args, **kw)
    end = time.time()
    print('%s executed in %s ms' % (fn.__name__, end - start))
    return fn(*args, **kw)
return wrapper

运行结果： fast executed in 0.0020651817321777344 ms slow executed in 0.12413549423217773 ms