python中difflib模块祥解

一 difflib模块
difflib模块：是提供的类和方法用来进行序列的差异化比较，它能够比对文件并生成差异结果文本或者html格式的差异化比较页面
1） Differ：以文本格式显示结果

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. Beautifu  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)



#以文本方式展示两个文本的不同:
d = difflib.Differ()
result = list(d.compare(text1, text2))
result = " ".join(result)
print(result)

其中 + - 号表示有差异行，？为下标显示
2） HtmlDiff：以html方式显示结果

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. Beautifu  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)
#以html方式展示两个文本的不同， 浏览器打开:
d = difflib.HtmlDiff()
with open("passwd.html", 'w') as f:
    f.write(d.make_file(text1, text2))

用颜色高亮显示文本的增加，删除或者更改
3） context_diff：返回一个差异文本行的生成器

from difflib import context_diff

import sys

s1 = ['bacon\n', 'eggs\n', 'ham\n', 'guido\n']
s2 = ['python\n', 'eggy\n', 'hamster\n', 'guido\n']
for line in context_diff(s1, s2, fromfile='before.py', tofile='after.py'):
    sys.stdout.write(line)  

对于字符串列表进行比较，可以看出只有第四个元素是相同的
假使s1 = ['eggs\n', 'ham\n', 'guido\n']为三个元素
则结果为：

每个元素会依次进行比较，而不是按照索引进行比较
4） get_close_matches：返回最大匹配结果的列表

from difflib import get_close_matches

d=get_close_matches('appel', ['ape', 'apple', 'peach', 'puppy'])
print(d)

返回的是与对象相似的所有元素的列表
5） ndiff：返回一个文本格式的差异结果

from difflib import ndiff

diff = ndiff('one\ntwo\nthree\n'.splitlines(1),
              'ore\ntree\nemu\n'.splitlines(1))
print(''.join(diff))

6） restore：返回一个由两个比对序列产生的结果

from difflib import ndiff, restore

diff = ndiff('one\ntwo\nthree\n'.splitlines(1),
              'ore\ntree\nemu\n'.splitlines(1))
diff = list(diff) # materialize the generated delta into a list
print(''.join(restore(diff, 1)))

假使print(''.join(restore(diff, 2))

因只有两个列表，不能再大于2了，表示的是列表数
二 简单应用
比较 /etc/passwd 和 /tmp/passwd 两个文件内容的不同

import  difflib


file1 = '/etc/passwd'
file2 = '/tmp/passwd'


with open(file1)  as f1, open(file2) as f2:
    text1 = f1.readlines()
    text2 = f2.readlines()

d = difflib.HtmlDiff()
with open("passwd.html", 'w') as f:
    f.write(d.make_file(text1, text2))

利用difflib模块来比较两个文件的不同，同时使用html格式高亮显示