Find and Edit SubElement in XML using Python ElementTree

Question

Because the XML file I'm dealing with has inconsistent subelements I'm having some difficulty finding and editing a specific subelement that doesn't appear in the series of elements until further down the file. I'm using Python's ElementTree included with Python 2.7.1.

Here's an example of the type of XML file I'm dealing with:

<?xml vin="1.0" encoding="UTF-8" standalone="yes"?>

<whatever id='Subaru' YouCanDriveMyCar='Wednesday' transmission='stick'>
        <model id='Ford' year='1972'>A</model>
        <model id='Chevrolet' vin="1234567890" stereo='Alpine' airconditioning='notworking'>Volt</model>
        <model id='Dodge' vin="3456789012" airconditioning='working'>Durango</model>
        <model id='Mercedes' vin="4567890123" airconditioning='none'>S150</model>
        <model id='BMW'>M350</model>
        <model id='Volkswagen' vin="5678901234" stereo='Sony'>Beetle</model>
        <model id='Honda' vin="6789012345" airconditioning="blowsicecubes">Accord</model>
</whatever>

In this example, I want to locate model id='Volkswagen' and change stereo='Sony' to 'Blaupunkt'.

If I use ElementTree to search for attribute 'stereo' it errors out because 'stereo' isn't contained in the elements at the top of the file.

Any help or hints would be greatly appreciated.

Martijn Pieters · Accepted Answer · 2013-03-03 18:16:28Z

3

Use a simple XPath expression to find the right model:

volkswagen = tree.find('.//model[@id="Volkswagen"]')

then simply adjust the stereo attribute:

volkswagen.set('stereo', 'Blaupunkt')

You could also search for model elements with a stereo attribute:

models_with_stereos = tree.findall('.//model[@stereo]')

then filter further on those elements.

If you switch to using lxml (an alternative implementation of the ElementTree API) you can use more complex XPath expressions still, including matching only model elements with id="Volkswagen" and a stereo attribute.

edited Mar 3, 2013 at 18:16

answered Mar 3, 2013 at 18:04

Martijn Pieters

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1 Comment

Don Bailey Over a year ago

Thank you so much Martijn! It worked and got me much closer to a solution. I'm working on a Windows platform and have looked at lxml, but it seems Windows is a bit of a pain to configure lxml properly. I will definitely take a look at lxml once I have more time. For the time being, your solution works fine! Thanks again.

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