Python while True循环中break无法正常退出程序问题排查

• 使用Python开发自行车租赁程序的小型用户面板，预期交互逻辑为：用户按下数字选项6时程序终止
• 实际运行异常：首次打开面板时选项6功能正常；但按下其他数字执行对应功能后，程序会在功能执行完毕等待20秒自动重新打开面板，此时再按下选项6，仅会重启面板，无法终止程序

def user_panel():
    """
    User panel to navigate through the program.
    """
    print(colored('\nWelcome to the bike rental program!', 'green', attrs=['bold', 'underline']))
    print('\nPlease select an option:\n1. Rent a bike\n2. Dock a bike\n3. Display the stations\n4. Summary\n5. Execute the maintenance of the defective bikes\n',colored('\r6. Exit', 'red', attrs=['bold']))
    while True:
        try:
            choice = int(input('\nEnter your choice: '))
            if choice == 1:
                rent_bike()
                print("Showing panel in 20 seconds...")
                time.sleep(20)
                print("Executing the user panel...")
                time.sleep(2)
                user_panel()
            elif choice == 2:
                dock_bike()
                print("Showing panel in 20 seconds...")
                time.sleep(20)
                print("Executing the user panel...")
                time.sleep(2)
                user_panel()
            elif choice == 3:
                display_stations()
                print("Showing panel in 20 seconds...")
                time.sleep(20)
                print("Executing the user panel...")
                time.sleep(2)
                user_panel()
            elif choice == 4:
                summary()
                print("Showing panel in 20 seconds...")
                time.sleep(20)
                print("Executing the user panel...")
                time.sleep(2)
                user_panel()
            elif choice == 5:
                maintenance_defective_bikes()
                print("Showing panel in 20 seconds...")
                time.sleep(20)
                print("Executing the user panel...")
                time.sleep(2)
                user_panel()
            elif choice == 6:
                print(colored('\nThank you for using the bike rental program!', 'red', attrs=['reverse']))
                break
            else:
                print(colored('\nPlease enter a valid choice!', 'red', attrs=['bold']))
                user_panel()
        except ValueError:
            print(colored('\nPlease enter a valid choice!', 'red', attrs=['bold']))
            user_panel()

问题根源是代码同时使用了while True无限循环和递归调用user_panel()的逻辑，导致调用栈嵌套：

• 每次执行完1-5号功能、输入无效选项、触发值错误时，代码都会递归调用新的user_panel()实例，每一层实例都持有独立的while True循环
• 选项6触发的break仅能跳出当前层user_panel()实例的循环，执行权会回到调用栈下层的旧user_panel()实例中，下层的无限循环会继续运行，表现为选6后无法退出、仅返回上层面板

移除函数内冗余的while True循环即可修复问题。递归调用本身已经实现了面板自动重载的逻辑，叠加while循环会造成多层调用栈嵌套，break无法穿透多层调用栈终止所有循环，移除后选项6的退出逻辑可正常生效。

内容的提问来源于stack exchange，提问作者Mathu_lmn