import time
print('按下回车开始计时，按下 Ctrl + C 停止计时。')
while True:
    input("")  
    starttime = time.time()
    print('开始')
    try:
        while True:
            print('计时: ', "{:.2f}".format(time.time() - starttime), '秒', end="\r")
            time.sleep(0.1)
    except KeyboardInterrupt:
        print('结束')
        endtime = time.time()
        print('总共的时间为:', round(endtime - starttime, 2),'secs')
        break