Python：匹配用户名和密码；如果密码不正确则提示输入密码；

Question

我正在尝试创建一个登录名。

我不知道如何创建/导入用户名和密码库；我目前正在研究寻找答案，但无论如何都问了。

• 将用户名与密码进行匹配（部分解决；需要添加多个具有匹配密码的用户名）。

• 如果密码不正确，如何创建循环？如果输入的密码不正确，则需要再次提示用户输入密码。

如何将循环限制为一定次数的密码尝试。

以下是我尝试过的：

def check_password(user, password):
    """ Return True if the user/pass combo is valid and False otherwise. """

    # Code to lookup users and passwords goes here.  Since the question
    # was only about how to do a while loop, we have hardcoded usernames
    # and passwords.
    return user == "pi" and password == "123"

def login():
    """ Prompt for username and password, repeatedly until it works.
    Return True only if successful.
    """

    try:
        while True:
            username = raw_input('username:')
            password = raw_input('password:')
            if check_password(username, password):
                break
            else:
                print "Please try again"

        print "Access granted"
        return True
    except:
        return False

用于测试：login()。

这修复了由于使用 return 而不是 print 导致密码错误时缺少循环提示的问题；和 if 而不是 while。

def login():
    #create login that knows all available user names and match to password ; if password is incorect returns try again and propmts for password again# 
    username = raw_input('username:')
    if username !='pi':
        #here is where I would need to import library of users and only accept those usernames; needs to be like 'pi' or 'bob' or 'tim'etc.
        print'user not found'
        username = raw_input('username')
    password = raw_input('password:')
    #how to match password with user? store in library ? 
    while password != '123':
        print 'please try again' # You have to change the 'return' to 'print' here
        password = raw_input('password')        
    return 'access granted'
    #basically need to create loop saying 'try again' and prompting for password again; maybe smarter to ask limited number of
    #times before returning 'you have reached limit of attempts#
    if password == '123':
        #again matching of passwords and users is required somehow 
        return 'access granted'

>>> login()
username:wronguser
user not found
usernamepi
password:wrongpass
please try again
password123
'access granted'
>>> 

感谢 Merigrim，更新之前的第一次尝试：

def login():

    # Create login that knows all available user names and match to password;
    # if password is incorect returns try again and propmts for password again# 
    username = raw_input('username:')
    if username !='pi':
        # Here is where I would need to import library of users and only 
        # accept those usernames; needs to be like 'pi' or 'bob' or 'tim'etc.
        return 'user not found'

    password = raw_input('password:')

    # How to match password with user? store in library? 
    if password != '123':
        return 'please try again'
    
    password = raw_input('password:')
    if password != '123':
        return 'please try again'

    # Basically need to create loop saying 'try again' and prompting 
    # for password again; maybe smarter to ask limited number of
    # times before returning 'you have reached limit of attempts

    elif password == '123':
        # Again matching of passwords and users is required somehow 
        return 'access granted'

这是它当前的工作原理：

>>> login()
username:pi
password:123
'access granted'
>>> login()
username:pi
password:wrongpass
'please try again'

我需要创建循环以再次提示输入密码。

Answer 1

您想要的是 while 语句。

不要像这样嵌套 if 语句：

if password != '123':
    return 'please try again'
    password = raw_input('password:')
    if password != '123':
        return 'please try again'
elif password == '123':
    return 'access granted'

您可以这样做：

while password != '123':
    print 'please try again' # You have to change the 'return' to 'print' here
    password = raw_input('password:')
return 'access granted'

这将继续提示用户输入密码，直到输入正确的密码。如果您想更熟悉 while 语句，我建议您查看一些教程，例如这个< /a>.
请注意，如果您返回某些内容，该函数将在那里退出，因此永远不会提示用户输入密码。在上面的代码中，我将返回更改为打印语句。

Answer 2

这是另一个解决方案，其中提取了用户名和密码，并提供了一个异常处理程序，以防有人试图中止输入。

另外，仅供参考，最好将用户名和密码放在一起，以免黑客知道什么是有效用户名，什么不是有效用户名。

def check_password(user, password):
    """ Return True if the user/pass combo is valid and False otherwise. """

    # Code to lookup users and passwords goes here.  Since the question
    # was only about how to do a while loop, we have hardcoded usernames
    # and passwords.
    return user == "pi" and password == "123"

def login():
    """ Prompt for username and password, repeatedly until it works.
    Return True only if successful.
    """

    try:
        while True:
            username = raw_input('username:')
            password = raw_input('password:')
            if check_password(username, password):
                break
            else:
                print "Please try again"

        print "Access granted"
        return True
    except:
        return False

# For testing
login()