Python生成随机字符串并保存到TXT文档中

使用JMeter做web多用户压力测试时，需要导入CSV文件（随机包含多个用户信息），用python自动生成

import random
import string

num = 1
while num < 100:
    username = ''.join(random.sample(['0','1','2','3','4','5','6','7','8','9','z','y','x','w','v','u','t','s','r','q','p','o','n','m','l','k','j','i','h','g','f','e','d','c','b','a'],5))
    password = random.randint(10000,99999)
    txt= str(username) + "," + str(password) + "\n"
    num +=1
    with open("user.txt","a") as f:
        f.write(txt)
print(num)