如果我们想要毫秒级的精确度，我们需要先将经过的秒数乘以1000，得到毫秒数，然后重复divmod计算，得到当前时间的分、秒和毫秒数，并减少睡眠时间（在Windows中，非常短的睡眠调用不是很精确，所以这可能无法按预期工作）：

import time

def countdown(time_sec):

    time_msec = time_sec*1000 # Turn received seconds into milliseconds
    
    while time_msec:
        
        mins, secs = divmod(time_msec, 60000) # Number of milliseconds in a minute
        secs, msecs = divmod(secs, 1000) # Number of milliseconds in a second

        timeformat = '{:02d}:{:02d}.{:03d}'.format(mins, secs, msecs) # Added another field to the format

        print(timeformat, end='\r')

        time.sleep(1/1000) # Reduced sleep length

        time_msec -= 1

    print("stop")

countdown(180)

现在打印：

02:57.292