练习1: 随机产生注册用账号

需求：

产生的账号是以@163.com结尾，长度由用户输入，产生多少条也由用户输入，用户名不能重复，用户名必须由大写字母、小写字母、数字组成

import random,string

def gen_username():
    endwith = '@163.com'
    success_username =0
    duplicate_flag = 0  # 密码是否重复
    duplicate_num = 0  # 重复的次数
    with open('usernamefile.txt', 'w') as fnew:  # 没有文件的话新建，已有会清空
        pass
    username_len = int(input('请输入用户名的长度：').strip())  #接收的为字符，需要转为int
    username_num = int(input('请输入产生账号的条数：').strip())
    while username_len <4:
        print('用户名必须由大写、小写、数字组成，长度必须大于3，请重新输入：')
        username_len = int(input('请输入用户名的长度：').strip())
    else:
        while success_username < username_num:
            username_list = []
            upper_name = random.choice(string.ascii_uppercase)
            lower_name = random.choice(string.ascii_lowercase)
            username_list.append(upper_name)
            username_list.append(lower_name)
            for digit_num in range(username_len-2):
                digit_name = random.randint(0,9)
                username_list.append(str(digit_name))  #要用到list 的join方法，list中的每个元素需为字符串
                digit_name +=1

            random.shuffle(username_list)  #打乱顺序
            username = ''.join(username_list) + endwith
            with open('usernamefile.txt','r') as f_dup:
                for line in f_dup:
                    if username == line:
                        duplicate_flag = 1
                        duplicate_num = duplicate_num + 1
                if duplicate_flag ==0:  #没有和文件里已有的用户名重复则写入
                    with open('usernamefile.txt','a+') as f_write:
                        f_write.write(username)
                        f_write.write('
')
                    success_username += 1
        else:
            print("用户名生成完成，重复次数 %d" % duplicate_num)

gen_username()