当要求输入时，我的布尔值要求在更改值之前重复输入

Question

我正在通过一个教程视频制作一个程序，代码是启动、停止或退出汽车。程序的一部分是这样做，如果汽车已经启动或停止，你在程序中告诉他们。我的程序会告诉用户汽车已经启动或停止，但在我告诉它停止两次之后，而不是一次。希望有人能描述一下while循环和if语句中的布尔值之间的关系？

action = ""
started = False
while action != 'exit':
    action = input("Type either start, stop, exit to work this car: ").lower()
    if action == "start":
        if started:
            print("The car is already started")
        else:
            started = True
            print("Congrats you started the car! You can now either stop the car or exit the car!")
            action == input("Type either stop or exit to work this car: ")  
    elif action == "stop":
        if not started:
            print("You already stopped the car")
        else:
            started = False
            print("Congrats you stopped the car! You can now exit the car!")
            action = input("Either start the car again or exit the car: ")
    elif action == "exit":
        print("Congrats you exited the car!")
        break
    else: 
        action = input("You typed an invalid response, type either start, stop or exit:")
pprint("The end")

Answer 1

让我更正你的密码

action = ""
started = 0 
while action != 'exit':
    action = input("Type either start, stop, exit to work this car: ").lower()
    if action == "start":
        if started:
            print("The car is already started")
        else:
            started = 2
            print("Congrats you started the car! You can now either stop the car or exit the car!")
            action = input("Type either stop or exit to work this car: ").lower()  
    elif action == "stop":
        if started == 2:
            started = 1
        elif started == 0:
            print("You already stopped the car")
        else:
            started = 0
            print("Congrats you stopped the car! You can now exit the car!")
            action = input("Either start the car again or exit the car: ").lower()
    elif action == "exit":
        print("Congrats you exited the car!")
        break
    else: 
        action = input("You typed an invalid response, type either start, stop or exit:").lower()
print("The end")

您需要更改action==input（…） 到操作=输入（…）

Answer 2

考虑汽车已经启动的情况，用户现在已经进入“停止”。这将我们置于else块中：

elif action == "stop":
    if not started:
        print("You already stopped the car")
    else:  # <-- here
        started = False
        print("Congrats you stopped the car! You can now exit the car!")
        action = input("Either start the car again or exit the car: ")

最后一行提示用户输入一个新命令，该命令将重置操作，并将您带回循环的顶部，您将立即提示用户输入一个新命令：

action = input("Type either start, stop, exit to work this car: ").lower()

换句话说，您的代码“忘记”用户在“stop”块中键入的内容，提示他们输入新命令，而不处理原始条目。

通过将第一个输入行移动到一个条件块（即else）中，可以很容易地解决这个问题。这样做的另一个好处是，您可以保持向用户提示适用于其情况的消息的准确性（例如，当用户刚刚输入“停止”时，“再次启动汽车或退出汽车”）。应该是这样的：

action = ""
started = False
while True:
    if action == "start":
        if started:
            print("The car is already started")
        else:
            started = True
            print("Congrats you started the car! You can now either stop the car or exit the car!")
        action = input("Type either stop or exit to work this car: ")  
    elif action == "stop":
        if not started:
            print("You already stopped the car")
        else:
            started = False
            print("Congrats you stopped the car! You can now exit the car!")
        action = input("Either start the car again or exit the car: ")
    elif action == "exit":
        print("Congrats you exited the car!")
        break
    else:
        if action:
            print("You typed an invalid response.")
        action = input("Type either start, stop, exit to work this car: ").lower()
print("The end")

注意，这在第一次通过时可以很好地工作，因为action=”“会直接将您带到新的else块。