求助:文本文件处理问题

工作上遇到问题，需要将配置文件做变更，因为数据有数千笔，无法手动修改，希望各位协助。

原本设定

dot1q pvc 2 profile pppoe encapsulation multi

bind interface m210.201.21 ericsson

bind authentication chap context ericsson maximum 8

更改后设定

dot1q pvc 2 profile pppoe encapsulation multi

bind subscriber erison-1-2-0-2@ericsson

bind authentication chap context ericsson maximum 8

subscriber erison-1-2-0- 最后** 2 与 dot1q pvc 2 相同

范例文件如下

dot1q pvc 2 profile pppoe encapsulation multi
  bind interface m210.201.21 ericsson
   bind authentication chap context ericsson maximum 8
dot1q pvc 3 profile pppoe encapsulation multi
  bind interface m203.79.236 ericsson
   bind authentication chap context ericsson maximum 8
dot1q pvc 5 profile pppoe encapsulation multi
  bind interface m210.201.13 ericsson
   bind authentication chap context ericsson maximum 8
dot1q pvc 14 profile pppoe encapsulation multi
  bind interface m210.201.21 ericsson
   bind authentication chap context ericsson maximum 8
dot1q pvc 3996 profile pppoe encapsulation multi
  bind interface m203.79.237 ericsson
   bind authentication chap context ericsson maximum 8
dot1q pvc 3997 profile pppoe encapsulation multi
  bind interface m203.79.237 ericsson
   bind authentication chap context ericsson maximum 8

    with open(filepath, 'r', encoding='utf-8') as rf:
        lines = rf.readlines()
        # print(lines)

    with open(filepath, 'w', encoding='utf-8') as wf:
        for index, line in enumerate(lines):
            if line.startswith('dot1q'):
                data = re.search(r'(?<=pvc\s)\d+', line).group()
                lines[index + 1] = 'bind subscriber erison-1-2-0-%s@ericsson\n'%data
        wf.writelines(lines)

Thank you very much.

根据提供的code修改
读取 example.txt，建立新的文件名 example1.txt，不会覆写源文件

import re

with open('example.txt', 'r', encoding='utf-8') as rf:
    lines = rf.readlines()
    # print(lines)

with open('example1.txt', 'w', encoding='utf-8') as wf:
    for index, line in enumerate(lines):
        if line.startswith('dot1q'):
            data = re.search(r'(?<=pvc\s)\d+', line).group()
            lines[index + 1] = 'bind subscriber erison-1-2-0-%s@ericsson\n' % data
    wf.writelines(lines)