Python怎么生成必带hr和erc的密码本

如题，Python生成一个8位的密码，里面必须包含hk 和ecr，另外的几位密码只包含数字和字母，并把所有的密码结果都输出到txt文档里面（一种密码占一行）。希望大佬给我整一个代码orz

import random
import os


digital=['1','2','3','4','5','6','7','8','9','0']
letter=['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y'\
    ,'z']
i=0
six_figures=str()
for i in range(6):
    six_figures=six_figures+random.choice(digital)
six_mixed=str()
i=0
for i in range(6):
    From=random.randint(1,2)
    if From==1:
        six_mixed=six_mixed+random.choice(digital)
    if From==2:
        six_mixed=six_mixed+random.choice(letter)
length=random.randint(7,15)
random_number=str()
i=0
for i in range(length ):
    random_number=random_number+random.choice(digital)
length=random.randint(7,15)
random_letters=str()
i=0
for i in range(length):
    From = random.randint(1, 2)
    if From == 1:
        random_letters = random_letters + random.choice(digital)
    if From == 2:
        random_letters = random_letters + random.choice(letter)
with open('密码.txt','w',encoding='UTF-8') as f:
    f.write('为您生成的六位数纯数字密码：'+six_figures)
    f.write('\n')
    f.write('为您生成的六位数混合密码：'+six_mixed)
    f.write('\n')
    f.write('为您生成的随机位数纯数字密码：'+random_number)
    f.write('\n')
    f.write('为您生成的随机位数混合密码：'+random_letters)
    f.write('\n')
print('密码生成完毕')
print('密码已保存至当前软件路径下的密码.txt文件中')
print('请不要轻易的将密码泄露给他人')
print('谢谢您的使用')
os.system('@pause')

这是思路!参考一下，要学会自己动脑。