code：

 1 f = open(‘yesterday‘,‘r‘,encoding=‘utf-8‘)
 2 f2 = open(‘yesterday.bak‘,‘w‘,encoding=‘utf-8‘)
 3 old_str = input(‘請輸入要修改的字符：‘)
 4 replace_str = input(‘請輸入替換成的字符:‘)
 5 for line in f.readlines():
 6     line = line.replace(old_str,replace_str)
 7     print(line)
 8     f2.write(line)
 9 f.close()
 
10 f2.close()

文件內容：（yesterday）

Somehow, it seems the love I knew was always the most destructive kind
不知為何，我經歷的愛情總是最具毀滅性的的那種
Yesterday when I was young
昨日當我年少輕狂
The taste of life was sweet
生命的滋味是甜的
As rain upon my tongue
就如舌尖上的雨露

感想：

　　思路很簡單就是打開源文件，然後循環，把源文件要替換的內容替換再寫入新文件！

Python-Day4實現簡單的shell sed替換功能