在一段时间内返回与起点不同的行答案

【问题标题】：Returning to a different line than the starting point within a while True-loop在一段时间内返回与起点不同的行
【发布时间】：2021-07-06 16:25:21
【问题描述】：

编辑：问题已在 cmets 中解决。没有试过勾选的答案。

当给出无效答案时，我使用了一个 while True-loop 来返回起点。这对我的第一个 if-elif-else-statement 非常有用。但是，如果我想要第二个 if-elif-else-statement，在前面的条件之一中，我无法弄清楚如何将无效答案发送回第二个 if-elif-else-statement 而不是第一个的开头。这是我的代码（问题以粗体显示）：

while True:
    a = input("Do you want Stackoverflow to help me with this problem? Yes/No: ")
    if a == "Yes":
        b = input("I need a second if-statement to make my point. Is that ok? Yes/No: ")
        if b == "Yes":
            print("How very nice of you. My problem is with the else condition")
            break
        elif b == "No":
            print("why not? I'm not asking for much")
            break
        else:
            print("Invalid answer. Write Yes/No.") #**Here is my problem. I want an invalid answer to return to line 4, not line 2.**
    elif a == "No":
        print("Ok. Thats too bad for me")
        break
    else:
        print("Invalid answer. Write Yes/No.")

【问题讨论】：

在第 4 行添加另一个 while True 然后修复其余代码的缩进
@mhhabib 这修复了它。我以为我已经尝试过这个并得到了错误，但我想不是。可能忘了修复缩进。谢谢！
查看代码，将其分解为几个函数可能是值得的。一种选择是将第二个循环放在一个单独的函数中，特别是如果你能给它一个好名字的话。另一个好方法是创建一个单独的函数，通过循环询问是/否问题，这样主代码就可以处理是/否，而无需担心循环。

标签： python python-3.x while-loop

【解决方案1】：

这可能不是有效的解决方案，但很容易理解和实施。

exit_first_loop = False
exit_second_loop = False

while not exit_first_loop:
    a = input("Do you want Stackoverflow to help me with this problem? Yes/No: ")
    if a == "Yes":
    
        while not exit_second_loop:
            b = input("I need a second if-statement to make my point. Is that ok? Yes/No: ")
            if b == "Yes":
                print("How very nice of you. My problem is with the else condition")
                exit_first_loop = True
                exit_second_loop = True
            elif b == "No":
                print("why not? I'm not asking for much")
                exit_first_loop = True
                exit_second_loop = True
            else:
                print("Invalid answer. Write Yes/No.") #**Now you will be sent to 4.**
    elif a == "No":
        print("Ok. Thats too bad for me")
        exit_first_loop = True
    else:
        print("Invalid answer. Write Yes/No.")

【讨论】：

【解决方案2】：

来自@mhhabib 评论：在第 4 行添加另一个 while True 然后修复其余代码的缩进

我还必须在第 14 行添加一个新的 break-statement 以获得所需的结果，在得到后停止循环。

固定代码，在#中进行了编辑。

while True:
    a = input("Do you want Stackoverflow to help me with this problem? Yes/No: ")
    if a == "Yes":
        while True: # added extra while True, and fixed indent.
            b = input("I need a second if-statement to make my point. Is that ok? Yes/No: ")
            if b == "Yes":
                print("How very nice of you. My problem is with the else condition")
                break
            elif b == "No":
                print("why not? I'm not asking for much")
                break
            else:
                print("Invalid answer. Write Yes/No.")
        break # added break (one indent back) so first loop doesnt start after second is broken.
    elif a == "No":
        print("Ok. Thats too bad for me")
        break
    else:
        print("Invalid answer. Write Yes/No."```

【讨论】：

【解决方案3】：

在代码组织方面，将代码重新组织成单独的函数可能是值得的；一种可能的分离功能是“循环询问，直到给出有效答案”；那么主代码根本不需要担心重试：

def ask(question, options):
    options_text = "/".join(options)
    while True:
        ans = input("%s %s:" % (question, options_text)
        if ans in options:
            return ans
        print("Invalid answer. Write %s" % options_text)

a = ask("Do you want Stackoverflow to help me with this problem?", ("Yes", "No"))
if a == "Yes":
    b = ask("I need a second if-statement to make my point. Is that ok?", ("Yes", "No"))
    if b == "Yes":
        print("How very nice of you. My problem is with the else condition")
    else:  # b == "No"
        print("why not? I'm not asking for much")
else:  # a == "No"
    print("Ok. Thats too bad for me")

【讨论】：