如何创建这个循环？ [复制]答案

【问题标题】：How do I create this loop? [duplicate]如何创建这个循环？ [复制]
【发布时间】：2019-11-18 21:32:44
【问题描述】：

如何创建这个循环，如果欢迎不等于“是”或“否”，它会重复问题（如果他们有帐户），但如果欢迎等于“是”或“否”，他们创建一个帐户（对于“否”）或允许用户登录（对于“是”）？

提前致谢

以下是我使用的代码：

welcome = input("Do you have an account? Please type either 'yes'/'no': ")        
if welcome == "no":
    while True:
        username  = input("OK. Let's create an account. Enter a username:")
        password  = input("Enter a password:")
        password1 = input("Confirm password:")
        if password == password1:
            file = open(username+".txt", "w")
            file.write(username+":"+password)
            file.close()
            welcome = "yes"
            break
        print("Passwords do NOT match!")

if welcome == "yes":
    while True:
        login1 = input("OK. Enter your username:")
        login2 = input("Enter your password:")
        file = open(login1+".txt", "r")
        data = file.readline()
        file.close()
        if data == login1+":"+login2:
            print("You have successfully logged in as, " + login1)
            print("")
            print("Welcome to the Music Quiz!")
            break
        print("Incorrect username or password.")

【问题讨论】：

标签： python python-3.3

【解决方案1】：

循环请求welcome。

while True:
    welcome = input("Do you have an account? Please type either 'yes'/'no': ")
    if welcome in ("yes", "no"):
        break
if welcome == "no":
    ...
else:
    ...

【讨论】：

非常感谢这有帮助

【解决方案2】：

您可以添加一个布尔变量来跟踪用户的输入状态（有效/无效）

validAnswer = False:
while not validAnswer:
    welcome = input("Do you have an account? Please type either 'yes'/'no': ")        
    if welcome == "no":
        validAnswer = True
        while True:
            username  = input("OK. Let's create an account. Enter a username:")
            password  = input("Enter a password:")
            password1 = input("Confirm password:")
            if password == password1:
                file = open(username+".txt", "w")
                file.write(username+":"+password)
                file.close()
                welcome = "yes"

                break
            print("Passwords do NOT match!")

    elif welcome == "yes":
        validAnswer = True
        while True:
            login1 = input("OK. Enter your username:")
            login2 = input("Enter your password:")
            file = open(login1+".txt", "r")
            data = file.readline()
            file.close()
            if data == login1+":"+login2:
                print("You have successfully logged in as, " + login1)
                print("")
                print("Welcome to the Music Quiz!")
                break
            print("Incorrect username or password.")

【讨论】：

非常感谢这有帮助

【解决方案3】：

您可以简单地将while True: 添加到整个内容中，这样，当输入“错误”输入时，它将通过两个if 子句并返回到循环的开头，它会再次提示用户。

while True:
    welcome = input("Do you have an account? Please type either 'yes'/'no': ")        
    if welcome == "no":
        while True:
            username  = input("OK. Let's create an account. Enter a username:")
            password  = input("Enter a password:")
            password1 = input("Confirm password:")
            if password == password1:
                file = open(username+".txt", "w")
                file.write(username+":"+password)
                file.close()
                welcome = "yes"
                break
            print("Passwords do NOT match!")

    if welcome == "yes":
        while True:
            login1 = input("OK. Enter your username:")
            login2 = input("Enter your password:")
            file = open(login1+".txt", "r")
            data = file.readline()
            file.close()
            if data == login1+":"+login2:
                print("You have successfully logged in as, " + login1)
                print("")
                print("Welcome to the Music Quiz!")
                break
            print("Incorrect username or password.")

【讨论】：