python3 文本文件字符串的替换

三种类型的替换：

1. 修改源文件：

 file_data = ""

with open(file,"r", encoading="utf-8") as f:

      for line in f:

            if old_str in line:

                  line = line.replace(old_str,new_str)

            file_data += line

with open(file,"w",encoding="utf-8") as f:

      f.write(file_data)

2. 把源文件内容经过修改后写到新文件中去

import os

 

with open(file,"r",encoding="utf-8") as f1, open("%s.bak" % file,"w", encoding="utf-8") as f2:

       for line in f1:

             if old_str in line:

                   line = line.replace(old_str,new_str)#replace只能对同一个line变量来做

             f2.write(line)

        os.remove(file)

        os.rename("%s.bak" % file,file)

 

3.使用正则表达式re.sub来替换

import re,os

 

with open(file,"r" encoding="utf-8") as f1,open("%s.bak"  % file, "w" ,encoding="utf-8") as f2:

       for line in f1:

              f2.write(re.sub(old_str,new_str,line))

       os.remove(file)

       os.rename("%s.bak"  % file,file)

alter("file1", "admin","password")