python 记录日志

import time
def show_info():
    print("输入提示文字，执行相应操作，0：退出  1，查看日志")
def write_loginfo():
    '''
    将用户名和登录时间写入日志
    :param username:用户名
    '''
    with open('log.txt','a') as f:
        string = '用户名：{} 登录时间：{}
'.format(username,time.strftime('%Y-%m-%d %H-%M-%S',time.localtime(time.time())))
        f.write(string)
def read_loginfo():
    '''读取日志'''
    with open('log.txt','r') as f:
        while True:
            line = f.readline()
            if line =='':
                break
            print(line)
if __name__ == '__main__':
    username = input("请输入用户名:")
    while len(username) <2:
        print('用户名不能少于2位！')
        username = input("请输入用户名:")
    password = input('请输入密码：')
    while len(password)<6:
        print("密码不能少于6位！")
        password = input('请输入密码：')
    print('登录成功')
    write_loginfo()
    show_info()
    num = int(input('输入操作数字：'))
    while True:
        if num ==0:
            print('退出成功!')
            break
        if num ==1:
            print('查看日志')
            read_loginfo()
            show_info()
            num = int(input('输入操作数字'))
        else:
            print('您输入的数字错误!')
            show_info()
            num = int(input('输入操作数字：'))