import time

class Stopwatch:
    def __init__(self):
        self.start_time = None
        self.elapsed_time = 0
        self.is_running = False
    
    def start(self):
        if not self.is_running:
            self.start_time = time.time()
            self.is_running = True
            print("秒表已开始")
    
    def pause(self):
        if self.is_running:
            self.elapsed_time += time.time() - self.start_time
            self.is_running = False
            print("秒表已暂停")
    
    def resume(self):
        if not self.is_running:
            self.start_time = time.time()
            self.is_running = True
            print("秒表继续运行")
    
    def reset(self):
        self.start_time = None
        self.elapsed_time = 0
        self.is_running = False
        print("秒表已重置")
    
    def get_time(self):
        if self.is_running:
            current_elapsed = self.elapsed_time + (time.time() - self.start_time)
        else:
            current_elapsed = self.elapsed_time
        
        # 将秒数转换为时:分:秒.毫秒格式
        hours = int(current_elapsed // 3600)
        minutes = int((current_elapsed % 3600) // 60)
        seconds = int(current_elapsed % 60)
        milliseconds = int((current_elapsed - int(current_elapsed)) * 1000)
        
        return f"{hours:02d}:{minutes:02d}:{seconds:02d}.{milliseconds:03d}"

def main():
    stopwatch = Stopwatch()
    
    while True:
        print("\n===== 秒表程序 =====")
        print(f"当前时间: {stopwatch.get_time()}")
        print("1: 开始/继续")
        print("2: 暂停")
        print("3: 重置")
        print("4: 退出")
        
        choice = input("请选择操作: ")
        
        if choice == '1':
            if stopwatch.is_running:
                stopwatch.resume()
            else:
                stopwatch.start()
        elif choice == '2':
            stopwatch.pause()
        elif choice == '3':
            stopwatch.reset()
        elif choice == '4':
            print("程序已退出")
            break
        else:
            print("无效输入，请重新选择")

if __name__ == "__main__":
    main()

1. Stopwatch类

我们创建了一个Stopwatch类来封装秒表的所有功能：

• __init__ - 初始化秒表状态
• start() - 开始计时
• pause() - 暂停计时
• resume() - 继续计时
• reset() - 重置秒表
• get_time() - 获取格式化后的时间

2. 时间计算原理

秒表的核心是计算经过的时间：

3. 时间格式化

我们使用以下方法将秒数转换为易读的格式：

# 计算小时、分钟、秒和毫秒
hours = int(current_elapsed // 3600)
minutes = int((current_elapsed % 3600) // 60)
seconds = int(current_elapsed % 60)
milliseconds = int((current_elapsed - int(current_elapsed)) * 1000)

# 格式化为 HH:MM:SS.ms
return f"{hours:02d}:{minutes:02d}:{seconds:02d}.{milliseconds:03d}"

===== 秒表程序 =====

当前时间: 00:00:00.000

1: 开始/继续

2: 暂停

3: 重置

4: 退出

请选择操作: