python修改文件中字符串并写入

# -*- coding: utf-8 -*-
#把文件内容替换
#把file3.txt 的 hello 替换为 good,并保存到file3Back.txt
import re

fp3=open("audio.txt","rb")
fp4=open("file4.txt","wb")

for s in fp3.readlines():#先读出来
fp4.write(s.replace("\n",",")) #替换 并写入

fp3.close()
fp4.close()