python模拟sed在每行添加##

     我们在平常的工作中有时候需要对摸一个文件进行操作，比如在一个文件的每行前面添加##之类的，在shell中这个需求很简单，用sed单行就能搞定，下面我们来看看一个文件：

[root@host-192-168-209-128 py-sed]# cat a.txt this is a text this is use for python this is also user for sed this is a end test file [root@host-192-168-209-128 py-sed]#

用sed的单行命令来搞定这个需求很简单，看下代码：

[root@host-192-168-209-128 py-sed]# sed 's/^/##/g' a.txt ##this is a text ##this is use for python ##this is also user for sed ##this is a end test file [root@host-192-168-209-128 py-sed]#

看看，果然够强大的sed啊，下面我来给大家介绍介绍如何用python实现这个有时候经常需要的操作，直接上代码了：

[root@host-192-168-209-128 py-sed]# cat a.py #!/usr/bin/env python with open('a.txt') as f:        con=f.readlines()        for i in range(0,len(con)):                print "###"+con[i].rstrip('\n')

代码实在很简单，看看效果如何吧：

[root@host-192-168-209-128 py-sed]# python a.py ###this is a text ###this is use for python ###this is also user for sed ###this is a end test file

呵呵，效果出来了吧，但是稍有缺陷，这个需要操作的对象文件我们是写死在代码里面的，如何把文件名作为参数传递给脚本呢，我们需要修改，以实现如下几个功能： 1. 需要把操作的文件作为参数传给脚本 2.需要对操作的对象进行判断，是否存在 3.如果脚本运行错误，需要有友好的提示效果 基于以上的需求，给出代码的最终版本,代码如下：

[root@host-192-168-209-128 py-sed]# cat tou.py #!/usr/bin/env python ''' edit by qhz Email : world77@163.coom This scrip to add "###" at every line for file ''' def usage():        print   ''' =============================================== This script to add "###" at every line for file Use Example: python script.py file =============================================== ''' import sys import os if len(sys.argv) == 2:         if os.path.isfile(sys.argv[1]):                 with open(sys.argv[1]) as f:                        con=f.readlines()                        for i in range(0,len(con)):                               print '###'+con[i].strip('\n')       else:                 print "==============================================="                  print "Your input file name is not exit or not correct"                  print "Please try again ,bye ..."                  print "===============================================" else:           usage()           exit() [root@host-192-168-209-128 py-sed]#

下面来看看各种情况和效果：

[root@host-192-168-209-128 py-sed]# python tou.py =============================================== This script to add "###" at every line for file Use Example: python script.py file =============================================== [root@host-192-168-209-128 py-sed]# python tou.py a.tx =============================================== Your input file name is not exit or not correct Please try again ,bye ... =============================================== [root@host-192-168-209-128 py-sed]# python tou.py a.txt ###this is a text ###this is use for python ###this is also user for sed ###this is a end test file [root@host-192-168-209-128 py-sed]#

    好了，这次的python介绍就到这里，我将为大家陆续模拟一些sed的简单功能，希望大家能喜欢