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Python模擬sed在每行添加##

我們在平常的工作中有時候需要對摸一個文件進行操作,比如在一個文件的每行前面添加##之類的,在shell中這個需求很簡單,用sed單行就能搞定,下面我們來看看一個文件:

[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的單行命令來搞定這個需求很簡單,看下代碼:

[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,果然夠強大的sed啊,下面我來給大家介紹介紹如何用python實現這個有時候經常需要的操作,直接上代碼了:

[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')

代碼實在很簡單,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,效果出來了吧,但是稍有缺陷,這個需要操作的對象文件我們是寫死在代碼裡面的,如何把文件名作為參數傳遞給腳本呢,我們需要修改,以實現如下幾個功能:
1. 需要把操作的文件作為參數傳給腳本
2.需要對操作的對象進行判斷,是否存在
3.如果腳本運行錯誤,需要有友好的提示效果
基於以上的需求,給出代碼的最終版本,代碼如下:


[root@host-192-168-209-128 py-sed]# cat tou.py
#!/usr/bin/env python
'''
edit by qhz
Email : [email protected]
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]#


下面來看看各種情況和效果:
[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,這次的python介紹就到這裡,我將為大家陸續模擬一些sed的簡單功能,希望大家能喜歡

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