Python and XML: update specific value

Question

I have to work with some XML file which seems weirdly sparse compared to what I saw in tutorials.

    <A>
       <B>
          <C>text<C>
          <D>text2<D>
          <E a=v1 b=v2>
             <F>v3</F>
          </E>
       </B>
   </A>

How to modify the value of v1, v2 and v3?

It depends on the library and your use of it. What have you tried so far? Also, I'm asserting that "weirdly parse" is a typo and should actually be "weirdly sparse", yes? — jrd1, Apr 20 '23 at 17:44
jrd1 yes typo. I was planning to use ElementTree as it seems to be the most use library in my team after that, whatever does the job. I'll take a look @Yitzhak Khabinsky's solution tomorrow (XLST). — Benji_90210, Apr 20 '23 at 22:27

score 3 · Answer 1 · edited Apr 23 '23 at 02:57

Here is how to do it by using XSLT.

It is using a so called Identity Transform pattern.

I had to fix the XML sample to make it well-formed:

Opening and closing XML elements were not matching.
Attribute values were not enclosed by quotes.

Input XML

<A>
    <B>
        <C>text</C>
        <D>text2</D>
        <E a="v1" b="v2">
            <F>v3</F>
        </E>
    </B>
</A>

XSLT

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="xml" indent="yes" encoding="utf-8"
                omit-xml-declaration="yes"/>
    <xsl:strip-space elements="*"/>

    <xsl:param name="v1" select="'v1_new'"/>
    <xsl:param name="v2" select="'v2_new'"/>
    <xsl:param name="v3" select="'v3_new'"/>

    <!--Identity Transform pattern-->
    <xsl:template match="@*|node()">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()"/>
        </xsl:copy>
    </xsl:template>

    <xsl:template match="E/@a">
        <xsl:attribute name="a">
            <xsl:value-of select="$v1"/>
        </xsl:attribute>
    </xsl:template>

    <xsl:template match="E/@b">
        <xsl:attribute name="b">
            <xsl:value-of select="$v2"/>
        </xsl:attribute>
    </xsl:template>

    <xsl:template match="F/text()">
        <xsl:value-of select="$v3"/>
    </xsl:template>
</xsl:stylesheet>

Output XML

<A>
  <B>
    <C>text</C>
    <D>text2</D>
    <E a="v1_new" b="v2_new">
      <F>v3_new</F>
    </E>
  </B>
</A>

Python

import os
import lxml.etree as ET

inputfile = "D:\\temp\\input.xml"
xsltfile = "D:\\temp\\process.xslt"
outfile = "D:\\output\\output.xml"

dom = ET.parse(inputfile)
xslt = ET.parse(xsltfile)
transform = ET.XSLT(xslt)
newdom = transform(dom,
              v1=XSLT.strparam("bk101"),
              v2=XSLT.strparam("New Author"))
infile = unicode((ET.tostring(newdom, pretty_print=True)))
outfile = open(outfile, 'a')
outfile.write(infile)

Lxml has the [write_output](https://lxml.de/api/lxml.etree._XSLTResultTree-class.html#write_output) method from XSLT result tree: `newdom.write_output(outfile)` (to replace last three lines). — Parfait, Apr 23 '23 at 03:01

Python and XML: update specific value

1 Answers1