1. difflib模块简介

difflib为python的标准库模块，无需安装。
作用是对比文本之间的差异。并且支持输出可读性比较强的HTML文档，与Linux下的diff命令相似。在版本控制方面非常有用。

2. difflib模块用法

用法	说明
splitlines()	按照行(’\r’, '\r\n’, \n’)分隔，返回一个包含各行作为元素的列表，如果参数 keepends 为 False，不包含换行符，如果为 True，则保留换行符。
difflib.Differ()	用于过滤函数（或None），默认值是None
d.compare(a,b)	比较两个行序列，并生成delta（一系列行）
difflib.HtmlDiff()	可以用于创建一个完整HTML文件，该文件显示具有行间和行内更改突出的文本的逐行比较
d.make_file(text1,text2)	比较a和b（字符串列表）并返回一个字符串，该字符串是一个完整的HTML文件，其中包含一个表格，显示逐行差异，突出显示行间和行内更改

3. 符号理解

符号	含义
'-’	包含在第一个系列行中，但不包含第二个
'+’	包含在第二个系列行中，但不包含第一个
’ ’	两个系列行一致
'?’	存在增量差异
'^’	存在差异字符

4. 实现文本对比

import difflib
text1 = '''  1. Beautiful is better than ugly.
       2. Explicit is better than implicit.
       3. Simple is better than complex.
       4. Complex is better than complicated.
		'''.splitlines(keepends=True)
text2 = '''  1. Beautiful is better than ugly.
       3.   Simple is better than complex.
       4. Complicated is better than complex.
       5. Flat is better than nested.
     '''.splitlines(keepends=True)

d = difflib.Differ()
print(''.join(list(d.compare(text1,text2))))

输出结果：

    1. Beautiful is better than ugly.
-        2. Explicit is better than implicit.
-        3. Simple is better than complex.
+        3.   Simple is better than complex.
?          ++
-        4. Complex is better than complicated.
?                 ^                     ---- ^
+        4. Complicated is better than complex.
?                ++++ ^                      ^
- 		+        5. Flat is better than nested.
+

用html方式对比

import difflib
text1 = '''  1. Beautiful is better than ugly.
       2. Explicit is better than implicit.
       3. Simple is better than complex.
       4. Complex is better than complicated.
		'''.splitlines(keepends=True)
text2 = '''  1. Beautiful is better than ugly.
       3.   Simple is better than complex.
       4. Complicated is better than complex.
       5. Flat is better than nested.
     '''.splitlines(keepends=True)

d = difflib.HtmlDiff()
htmlContent = d.make_file(text1,text2)
# print(htmlContent)
with open('diff.html','w') as f:
    f.write(htmlContent)

输出结果：

5. linux文件之间的对比

import difflib
filename1 = '/tmp/passwd'
filename2 = '/tmp/passwd1'

with open(filename1) as f1,open(filename2) as f2:
    content1 = f1.read().splitlines(keepends=True)
    content2 = f2.read().splitlines(keepends=True)

d = difflib.HtmlDiff()
htmlcontent = d.make_file(content1,content2)
with open('passwdDiff.html','w') as f:
    f.write(htmlcontent)

输出结果：

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