{"id":3225,"date":"2014-10-06T02:07:37","date_gmt":"2014-10-06T02:07:37","guid":{"rendered":"http:\/\/dalelane.co.uk\/blog\/?p=3225"},"modified":"2014-10-06T02:26:30","modified_gmt":"2014-10-06T02:26:30","slug":"comparing-xml-files-ignoring-order-of-attributes-and-child-elements","status":"publish","type":"post","link":"https:\/\/dalelane.co.uk\/blog\/?p=3225","title":{"rendered":"Comparing XML files ignoring order of attributes and child elements"},"content":{"rendered":"

I need to diff some XML files. <\/p>\n

For these particular XML files, order is not important. The XML is being used to contain a set of things, not a list – the order of the elements has no significance. Similarly, the order of the attributes within each element isn’t significant. <\/p>\n

For example, for my purposes, these two XML files are equivalent:<\/p>\n

<myroot>\r\n    <mychild id=\"123\">\r\n        <fruit>apple<\/fruit>\r\n        <test hello=\"world\" brackets=\"angled\" question=\"answers\"\/>\r\n        <comment>This is a comment<\/comment>\r\n    <\/mychild>\r\n    <mychild id=\"456\">\r\n        <fruit>banana<\/fruit>\r\n    <\/mychild>\r\n    <mychild id=\"789\">\r\n        <fruit>orange<\/fruit>\r\n        <test brackets=\"round\" hello=\"greeting\">\r\n            <number>111<\/number>\r\n        <\/test>\r\n        <dates>\r\n              <modified>123<\/modified>\r\n              <created>253<\/created>\r\n              <accessed>44<\/accessed>\r\n        <\/dates>\r\n    <\/mychild>\r\n<\/myroot><\/pre>\n
<myroot>\r\n    <mychild id=\"789\">\r\n        <fruit>orange<\/fruit>\r\n        <test hello=\"greeting\" brackets=\"round\">\r\n            <number>111<\/number>\r\n        <\/test>\r\n        <dates>\r\n              <accessed>44<\/accessed>    \r\n              <modified>123<\/modified>\r\n              <created>253<\/created>\r\n        <\/dates>\r\n    <\/mychild>\r\n    <mychild id=\"123\">\r\n        <test question=\"answers\" hello=\"world\" brackets=\"angled\"\/>\r\n        <comment>This is a comment<\/comment>\r\n        <fruit>apple<\/fruit>\r\n    <\/mychild>\r\n    <mychild id=\"456\">\r\n        <fruit>banana<\/fruit>\r\n    <\/mychild>\r\n<\/myroot><\/pre>\n
I needed to compare some large XML files, which have big differences in the order of elements, and I couldn’t find a tool that would do the job. So I wrote a bit of Python to do it for me.<\/p>\n
<\/p>\n
How it works<\/h3>\n
I cheated. <\/p>\n
Diff tools are complex, and I’m in a hurry without time to implement one. <\/p>\n
Instead, to compare two of my XML files, my approach is to sort them both so they have a consistent order, and then diff the sorted files using an existing visual diff tool. (On Windows, I prefer vsdiff<\/code> from SlickEdit<\/a>. On Mac, I prefer diffmerge<\/a>. My approach works with either of these.)<\/p>\n
Example<\/h3>\n
For example, consider the following simple test files:<\/p>\n
testA.xml<\/p>\n
<myroot>\r\n    <mychild id=\"123\">\r\n        <fruit>apple<\/fruit>\r\n        <test hello=\"world\" testing=\"removed\" brackets=\"angled\" question=\"answers\"\/>\r\n        <comment>This is a comment<\/comment>\r\n    <\/mychild>\r\n    <mychild id=\"456\">\r\n        <fruit>banana<\/fruit>\r\n        <comment>This will be removed<\/comment>\r\n    <\/mychild>\r\n    <mychild id=\"789\">\r\n        <fruit>orange<\/fruit>\r\n        <test brackets=\"round\" hello=\"greeting\">\r\n            <number>111<\/number>\r\n        <\/test>\r\n        <dates>\r\n              <modified>123<\/modified>\r\n              <created>880<\/created>\r\n              <accessed>44<\/accessed>\r\n        <\/dates>\r\n    <\/mychild>\r\n<\/myroot><\/pre>\n
testB.xml<\/p>\n
<myroot>\r\n    <mychild id=\"789\">\r\n        <fruit>orange<\/fruit>\r\n        <test hello=\"greeting\" brackets=\"round\">\r\n            <number>111<\/number>\r\n        <\/test>\r\n        <dates>\r\n              <accessed>49<\/accessed>    \r\n              <modified>123<\/modified>\r\n              <created>253<\/created>\r\n        <\/dates>\r\n    <\/mychild>\r\n    <mychild id=\"123\">\r\n        <test question=\"answers\" hello=\"world\" brackets=\"angled\"\/>\r\n        <comment>This is a comment<\/comment>\r\n        <fruit>apple<\/fruit>\r\n    <\/mychild>\r\n    <mychild id=\"456\">\r\n        <fruit>banana<\/fruit>\r\n    <\/mychild>\r\n<\/myroot><\/pre>\n
On Mac, I run:
\n$ python xmldiff.py diffmerge testA.xml testB.xml<\/code><\/p>\n
And get:
\n\"Screen<\/a><\/p>\n
On Windows, I run:
\n$ python xmldiff.py vsdiff testA.xml testB.xml<\/code><\/p>\n
And get:
\n\"screenshot-windows-20141006-0255\"\/<\/a><\/p>\n
Source<\/h3>\n
The source showing how this works is available in a gist at
\ngist.github.com\/dalelane<\/a>. <\/p>\n
It’s a quick hack to let me compare a handful of files, so it’s not been rigorously tested. But it’s a very simple little tool, and was good enough for my purposes tonight!<\/p>\n