文件比较的逻辑 [英] Logic for a file compare

问题描述

我试图写一个程序文件比较。例如：

I trying to write a programm for file compare. For example:

file1

1
2
3
4
5

file2

1
2
@
3
4
5

如果我逐行做，我得到：

If I do it line by line, I get:

1 == 1; 
2 == 2;
3 != @;
4 != 3;
5 != 4;
  != 5;

但是，事实上，文件之间的唯一区别是@。我想要这样的东西：

But, the truth is that the only difference between the files is @. I want get something like this:

1 == 1;
2 == 2;
  != @;
3 == 3;
4 == 4;
5 == 5;

这是最好的方法吗？没有使用任何外部应用程序，如diff，fc等。

Which is the best way to do it? without using any external application, such as diff, fc, etc.

推荐答案

Python有一个非常方便的库， a href =http://docs.python.org/library/difflib.html =nofollow noreferrer> difflib 。基础的SequenceMatcher类接受两个python序列，并给你（除其他外）一系列操作码，告诉你如何从第一个序列到第二个序列（即差异）。这些格式为：

Python has a very handy library for comparing sequences called difflib. The underlying SequenceMatcher class takes two python sequences and gives you (among other things) a sequence of opcodes telling you how you would get from the first sequence to the second (i.e. the differences). These are of the form:

• 将此块替换为


• 插入块
• 
  
• 删除块


• 复制块（称为等于）

这些引用块通过给原始序列赋予索引。这可以应用于文件中的行或字符串中的字符或任何其他可以转换为python中的序列。

These reference blocks by giving indices into the original sequences. This can be applied to lines in a file or characters in a string or anything else you can turn into a sequence in python.

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