我們在平常的工作中有時候需要對摸一個檔案進行操作，比如在一個檔案的每行前面新增##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檔案：
[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，看下程式碼：
[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，直接上程式碼了：
[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(`
`)
程式碼實在很簡單，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，這個需要操作的物件檔案我們是寫死在程式碼裡面的，如何把檔名作為引數傳遞給指令碼呢，我們需要修改，以實現如下幾個功能：
1. 需要把操作的檔案作為引數傳給指令碼
2.需要對操作的物件進行判斷，是否存在
3.如果指令碼執行錯誤，需要有友好的提示效果
基於以上的需求，給出程式碼的最終版本,程式碼如下：
[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(`
`)
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