课堂练习：python 简单登录

while True:
    username = input('name:').strip()
    password = input('passwd:').strip()
    if len(username) != 0 and len(password) != 0:

        with open('user_file','r',encoding='utf8') as f:
            log_sucess = False
            f.seek(0,0)
            for line in f.readlines():
                line = line.split()
                if len(line) != 0:
                    if username == line[0] and password == line[1]:
                        print('welcom %s'%username)
                        log_sucess = True
                    elif username == line[0] and password != line[1]:
                        print('密码错误')
                    else:
                        print('用户不存在')
            if log_sucess:
                break
    else:
        continue