实现简单的shell sed替换功能

import sys

f=open('lyrics.txt','r',encoding='utf-8')  #读写
f_new=open('lyrics_new','w+',encoding='utf-8')
find_str=sys.argv[1]
replace_str=sys.argv[2]
for line in f:
    if find_str in line:
        line=line.replace(find_str,replace_str)
    f_new.write(line)
f.close()
f_new.close()