Python：将用户名与/密码匹配；提示输入密码不正确；

Question

我正在尝试创建登录。

我不确定如何创建/导入用户名和密码库；我正在研究以找到答案，但无论哪种方式都问过。

匹配用户名和密码 //（部分解决；需要添加多个用户名和密码匹配）

如果密码不正确，如何创建循环？如果输入的密码不正确，需要再次提示用户输入密码。 //（已解决；使用 [print] 而不是 [return]）

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"

定义登录（）： """ 提示输入用户名和密码，重复直到成功。 仅在成功时返回 True。 """

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

登录（）

如果密码错误.*由于使用'return'而不​​是'print'，这个固定的缺少循环提示;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'

登录() 用户名：错误用户 未找到用户 用户名pi 密码：错误密码 请再试一次 密码123 '访问权限'

#更新前的第一次尝试感谢：Merigrim： 定义登录（）：

    # 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'

这是它目前的工作方式：

>>> 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。

而不是像这样嵌套 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'

你可以这样做：

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。如果您想更加熟悉 while 语句，我建议您查看一些教程，例如 this one。 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，我将返回改为打印语句。

Answer 2

这是另一个解决方案，其中包含用户名和密码，以及一个异常处理程序，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，以免让破解者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()