写代码： 编写登录接口

# 编写登录接口
# 基础需求：
# 1. 让用户输入用户名密码
# 2. 认证成功后显示欢迎信息
# 3. 输错三次后退出程序

# 升级需求：
# 1. 可以支持多个用户登录（提示, 通过列表存多个账户信息）
# 2. 用户3次认证失败后，退出程序，再次启动程序尝试登录时，还是锁定状态（提示：需把用户锁定的状态存到文件里）

==方法1==

# define a counter
count = 0

# define user and password map with dict
user_password = {'linda': '123', 'emily': '123', 'yu': '123'}

while True:
    login_user = input('Please enter your account: ')

    # Read the local_file.
    lock = open('local_file', 'r+')
    lock_file = lock.read().split()

    # Verify whether the user is locked or not.
    if login_user in lock_file:
        print('------------------------------------------------
'
              'Sorry, your account {} is locked.
'.format(login_user))
        continue
    # Verify the user exists or not.
    elif login_user not in user_password.keys():
        print('------------------------------------------------
'
              'Sorry, your account {} does not exist.
'.format(login_user))
        continue
    while True:
        login_pwd = input('Please enter your password: ')
        # Verify the password correct or not.
        if login_user in user_password.keys() and login_pwd in user_password.values():
            print("welcome {} to login!".format(login_user))
            exit()
        else:
            count += 1
            times = 3 - count
            if count == 3:
                print(
                    '------------------------------------------------
'
                    'Sorry, you already entered 3 times, the account is locked.
')
                # Write the account into lock_file
                lock.write('{}
'.format(login_user))
                # Close file
                lock.close()
                flag = True  # drop the second cycle
                break
            print(
                '------------------------------------------------
 '
                'Sorry, your password is not correct. You have {} times
'.format(times))
    if flag:
        break

　　==方法2==

try_times = 0
user_password = {'linda': '123', 'emily': '123', 'yu': '123'}

lock = open('lock_user.txt', 'r+')
lock_file = lock.read().split()

username = input("could you enter your name?: ")

if username in lock_file:
    print("your account is locked, could not login right now. ")
    exit()
else:
    while try_times < 3:

        password = input("please enter your password:")

        if username in user_password.keys() and password in user_password.values():
            print("welcome {} to login!".format(username))
            break
        elif username in user_password.keys() and password not in user_password.values():
            print("password is not correct")

        elif username not in user_password.keys():
            print("failed login with invalid username")

        try_times += 1

while try_times == 3:
    print("sorry, try 3 times, locked your account.")
    f = open("lock_user.txt", 'a')
    f.write('{}
'.format(username))
    f.close()
    break