文件操作总结(2)

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author:James Tao

#文件修改
#将文件更改之后写到新文件

find_str='我有太多歌曲永远不会被唱起'
replace_str='YOUTAIDUODEGEQUYONGYUANBUHUIBEICHANGQI'

f=open('yesterday','r',encoding='utf-8')#原文件
f_new=open('yesterday.bak','w',encoding='utf-8')#新文件
for line in f:#f为一个迭代器，按行迭代
    if find_str in line:
        line=line.replace(find_str,replace_str)#字符串替换replace函数
    f_new.write(line)
f.close()
f_new.close()


#用with打开文件,省去close步骤
with open('yesterday','r',encoding='utf-8') as f:
    for line in f:
        print(line)


#用with可以打开多个文件
find_str='我有太多歌曲永远不会被唱起'
replace_str='YOUTAIDUODEGEQUYONGYUANBUHUIBEICHANGQI'

with open('yesterday','r',encoding='utf-8') as f1, 
        open('yesterday.bak', 'w', encoding='utf-8') as f2:
    for line in f1:
        if find_str in line:
            line=line.replace(find_str,replace_str)
        f2.write(line)