显示密码错误的尝试次数，如果用户输入正确的密码则接受

Question

我一周前开始了我的编程之旅，之前的编码知识为零。 我还观看了有关如何发布堆栈溢出问题的视频，因此希望获得建设性反馈。

详情：

语言 - Python

版本 - 3.8.3

编辑器 - VS 代码

我正在尝试编写一个程序，该程序接受用户输入并检查它是否是有效密码。如果是，则显示“正确”并退出程序，如果不正确，则显示剩余尝试次数，总共3次，并再次要求输入。

我刚刚在我的教程中到达了 WHILE 循环部分，并用它来制作程序。

msg = input("What's the secret password: ")

# Password attempt is 3 times, starts at 2, then 1 and ends when counter is 0
num = 2  

# bananas is the correct password
while msg != "bananas":  
    if num == 0:
        print("Too many wrong attempts. You are locked out!")  # exhausted all 3 attempts, should print given message.

    else:
        print(f"Wrong Password! You have {num} chances left")  # password incorrect, display attempts left
        msg = input("What's the secret password: ")
        num = num - 1

print("Correct") 

问题

如果我立即运行它并提供正确的密码，或者在尝试 1-2 次失败后，它会按预期运行。 但是如果我输入错误 3 次，它就会进入显示消息的循环

错误尝试太多。你被锁定了！

并且永远打印出来。我无法弄清楚在哪里退出循环，以便它只显示一次消息并退出程序。

请帮助解决问题。

2 incorrect password, 1 correct in 3rd attempt

all 3 incorrect attempts

Answer 1

试试这个结构：

num = 3
while input("What's the secret password: ") != "bananas" and num-1 != 0:
    num -= 1
    print(f"Wrong Password! You have {num} chance" + ['_', ' ', 's '][num] + "left")
print("Correct") if num else print("Too many wrong attempts. You are locked out!")

输入可直接用于 while 条件 - 如果您还剩零次尝试或获得正确的密码，while 循环将中断，if num:（num 大于零 - True）会显示相应的消息。

作为一个函数：

def pswd_entry(num=3):
    while input("What's the secret password: ") != "bananas" and num-1 != 0:
        num -= 1
        print(f"Wrong Password! You have {num} chance" + ['_', ' ', 's '][num] + 
    "left")
    print("Correct") if num else print("Too many wrong attempts. You are locked 
    out!")

注意：pswd_entry(num=3) 有一个可选参数 num，如果留空则默认为 3。

---

解释

我们的尝试次数：

num = 3

While 循环

第一个条件： input("What's the secret password: ") != "bananas"

input() 将等到用户输入一个值，如果该值不是“bananas”，则 while 循环不会中断。

第二个条件： num-1 != 0

这将检查尝试次数（减一）不 (!=) 等于 0。

如果条件 1 and 满足条件 2，while 循环将运行。

减去一次尝试num -=1（与num = num -1 相同），然后写入剩余机会数的警告。

+['_', ' ', 's '][num] 将选择是否将's' 添加到机会/秒 - 例如，如果还剩 1 次机会（即 num = 1），则只需将 ' '（空格）添加到 'chance'

如果num = 2:

['_', ' ', 's '][2] - ([0 element, 1 element, 2 element][select 2 element]) = 's' 添加到chance -> chances

while input("What's the secret password: ") != "bananas" and num-1 != 0:
    num -= 1
    print(f"Wrong Password! You have {num} chance" + ['_', ' ', 's '][num] + "left")

最后 - 打印声明

print("Correct") if num else print("Too many wrong attempts. You are locked out!")

如果num !=0 的值if num 将执行print("Correct") - if 检查这里检查num 有一个值并且不为零（假） - 否则它将打印锁定消息（来自else)。

Answer 2

这里的代码不要重复输入语句

password, times = 'bananas', 3
while True:
    times -= 1
    msg = input("What's the secret password: ")
    if msg == password:
        print("Correct")
        break
    elif times > 0:
        print(f"Wrong Password! You have {times} chances left")
    else:
        print("Too many wrong attempts. You are locked out!")
        break

功能很好地将您的工作分成小部分。你可以找到这个和上面的区别。

def login(password, times=3):
    while True:
        times -= 1
        msg = input("What's the secret password: ")
        if msg == password:
            print("Correct")
            return True
        elif times > 0:
            print(f"Wrong Password! You have {times} chances left")
        else:
            print("Too many wrong attempts. You are locked out!")
            return False

result = login('bananas')
if result:
    print('Login sucessful !')
else:
    print('Login failed !')

Answer 3

通过将其放入函数中，您可以在打印后使用return 退出程序。

def main():
    msg = input("What's the secret password: ")

    # Password attempt is 3 times, starts at 2, then 1 and ends when counter is 0
    num = 2  

    # bananas is the correct password
    while msg != "bananas":  
        if num == 0:
            print("Too many wrong attempts. You are locked out!")  # exhausted all 3 attempts, should print given message.
            return
        else:
            print(f"Wrong Password! You have {num} chances left")  # password incorrect, display attempts left
            msg = input("What's the secret password: ")
            num = num - 1

    print("Correct")


main()