Compares two XML documents by diffing their text, ignoring structure, and wraps changed text in <del>/<ins> tags.
Project description
Compares the text inside two XML documents and marks up the differences with <del> and <ins> tags.
This is the result of about 7 years of trying to get this right and coded simply. I’ve used code like this in one form or another to compare bill text on GovTrack.us <https://www.govtrack.us>.
The comparison is completely blind to the structure of the two XML documents. It does a word-by-word comparison on the text content only, and then it goes back into the original documents and wraps changed text in new <del> and <ins> wrapper elements.
The documents are then concatenated to form a new document and the new document is printed on standard output. Or use this as a library and call compare yourself with two lxml.etree.Element nodes (the roots of your documents).
The script is written in Python 3 and uses Google’s Diff Match Patch library <https://code.google.com/p/google-diff-match-patch/>, as re-written and sped-up by @leutloff <https://github.com/leutloff/diff-match-patch-cpp-stl> and then turned into a Python extension module by me <https://github.com/JoshData/diff_match_patch-python>. (A great pull request would be to replace that dependency with Python’s built-in difflib <https://docs.python.org/3/library/difflib.html> module. It’ll be slower but then won’t have any unusual dependencies.)
Example
Comparing these two documents:
<html>
Here is <b>some bold</b> text.
</html>
and:
<html>
Here is <i>some italic</i> content that shows how <tt>xml_diff</tt> works.
</html>
Yields:
<documents>
<html>
Here is <b>some <del>bold</del></b><del> text</del>.
</html>
<html>
Here is <i>some <ins>italic</ins></i><ins> content that shows how </ins><tt><ins>xml_diff</ins></tt><ins> works</ins>.
</html>
</documents>
Installation
To install on Ubuntu follow these steps:
sudo apt-get install python3-lxml # or sudo apt-get install libxml2-dev libxslt1-dev sudo pip3 install lxml # get my Python extension module for the Google Diff Match Patch library # so we can compute differences in text very quickly git clone --recursive https://github.com/JoshData/diff_match_patch-python cd diff_match_patch-python sudo apt-get install python3-dev python3 setup.py build sudo python3 setup.py install
Running
Compare two XML documents:
python3 xml_diff.py --tags del,ins doc1.xml doc2.xml > with_changes.xml
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