import time, functools

def metric(fn):

    t = time.perf_counter()

    @functools.wraps(fn)#保证在修饰后fn.__name__不发生变化

    def decorator(*args,**kw):

        k=fn(*args,**kw)

        print('%s executed in %s ms' % (fn.__name__, time.perf_counter()-t))

        return k

    return decorator