difflib模块文件内容差异对比

简介    

      difflib作为python的标准库模块，无需安装，作用是比对文本之间的差异，且支持输出可读性比较强的HTML文档，与Linux下的diff命令相似。可以使用该模块比对代码和配置文件的差异，在版本控制方面非常有用。Python2.3以后的版本默认自带difflib模块，无需额外安装。

使用方法

• 字符串差异的比对

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


import difflib

text1 = """text1:
This module provides classes and functions for comparing sequences.
including HTML and context and unified diffs.
difflib document v7.4
add string
"""

text1_lines = text1.splitlines()

text2 = """text2:
This module provides classes and functions for Comparing sequences.
including HTML and context and unified diffs.
difflib document v7.5"""

text2_lines = text2.splitlines()

d = difflib.Differ() #创建Differ对象

diff = d.compare(text1_lines,text2_lines) #采用compare方法对字符串进行比较

print "\n".join(list(diff)) #join将序列中的元素以指定的字符连接生成一个新的字符串str.join(sequence)
结果显示
- text1:
?     ^

+ text2:
?     ^

- This module provides classes and functions for comparing sequences.
?                                                ^

+ This module provides classes and functions for Comparing sequences.
?                                                ^

  including HTML and context and unified diffs.
- difflib document v7.4
?                     ^

+ difflib document v7.5
?                     ^

- add string

     各个差异符号表示含义

'-':包含在第一个序列行中，不包含在第二个序列行中

'+':包含在第二个序列行中，不包含在第一个序列行中

'':两个序列行一致

'?':标志两个序列行存在增量差异

'^':标志出两个序列存在的差异字符

• 生成美观的HTML文档

采用HtmlDiff()的make_file()方法就可以生成美观的HTML文档，可以对上面的例子进行如下修改：

d = difflib.Differ() 
diff = d.compare(text1_lines,text2_lines) 
print "\n".join(list(diff)) 

　　将以上修改为

d = difflib.HtmlDiff()
diff = d.make_file(text1_lines,text2_lines)
print  diff

 将以上程序保存为sample2.py ,运行python sample2.py > diff.html，用浏览器打开保存的html文件

• 比对nginx配置文件差异

     当我们维护多个Nginx配置时，时长会比对不同版本配置文件的差异，使运维人员更加清晰地了解不同版本迭代后的更新项，实现的思路是读取两个需对比的配置文件，再以换行符作为分隔符，调用difflib.HtmlDiff()生成HTML格式的差异文档。具体实现如下：

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

import difflib
import sys

try:
    textfile1 = sys.argv[1]
    textfile2 = sys.argv[2]
except Exception,e:
    print "Error:" +str(e)
    print "Usage: python sample3.py filename1 filename2"
    sys.exit()

def readfile(filename):
    try:
        filehandle = open(filename,'rb')
        text = filehandle.read().splitlines()
        filehandle.close()
        return text
    except IOError as error:
        print ('Read file Error:' +str(error))
        sys.exit()

text1_lines = readfile(textfile1)
text2_lines = readfile(textfile2)

d = difflib.HtmlDiff()
print d.make_file(text1_lines,text2_lines)　　

   运行代码 ython sample3.py nginx.conf.v1  nginx.conf.v2 > sample3_diff.html 

通过浏览器查看两个文件差异

附nginx配置文件

nginx.conf.zip