python怎么实现计时

import time

print('按下回车开始计时，按下 Ctrl + C 停止计时。')

while True:

    try:

        input() # 如果是 python 2.x 版本请使用 raw_input()

        starttime = time.time()

        print('开始')

        while True:           

            print('计时: ', round(time.time() - starttime, 0), '秒', end="\r")

            time.sleep(1)

    except KeyboardInterrupt:

        print('结束')

        endtime = time.time()

        print('总共的时间为:', round(endtime - starttime, 2),'secs')

        break