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Asked: 2026-06-09T01:27:15+00:00

I’m trying to learn the basics of XML processing (with lxml) running Python 2.7.2.

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I’m trying to learn the basics of XML processing (with lxml) running Python 2.7.2. I’ve created a REALLY simple starting file, but it’s cratering. The code is:

from lxml import etree

doc = etree.parse('/Desktop/plc_dmt.xml')

print doc

I’ve tried variations on this code, using different xml files, and also opening the file first before executing the etree.parse() method, but they all yield a similar or identical error message, below:

Traceback (most recent call last):
  File "XMLparse_test.py", line 7, in <module>
    doc = etree.parse('/Users/Dad/Desktop/plc_dmt.xml')
  File "lxml.etree.pyx", line 2954, in lxml.etree.parse (src/lxml/lxml.etree.c:56220)
 ...   {Misc  error stuff}
 ... 
  lxml.etree.XMLSyntaxError: xmlParsePI : no target name, line 3, column 14

I confirmed that at least some of the XML files were well-formed, at least insofar as they ran correctly on a web server. I don’t understand the error message — What is the target name it is seeking?

Here’s the input xml file.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<response>
<heartbeat><?--#exec cmd_argument='printf( "0x%02X%02X", InReadUByte( 0 ), InReadUByte( 1 ))'-->    </heartbeat>

<dmt node="1">
    <address><?--#exec cmd_argument='printf( "0x%02X", InReadUByte( 20 ))'--></address>
    <status><?--#exec cmd_argument='printf( "0x%02X", InReadUByte( 21 ))'--></status>
    <realflow><?--#exec cmd_argument='printf( "%f", InReadFloat( 22 ))'--></realflow>
    <pressure><?--#exec cmd_argument='printf( "0x%02X%02X", InReadUByte( 26 ), InReadUByte( 27 ))'--></pressure>
    <temp><?--#exec cmd_argument='printf( "0x%02X%02X", InReadUByte( 28 ), InReadUByte( 29 ))'--></temp>
</dmt>
# Misc stuff pulled out to keep file shorter...
</response>

Much of the embedded code are Server Side Include commands for this web server, which is connected to some instrumentation. This file does operate correctly on the server.

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1 Answer

  1. Editorial Team

    Your XML is invalid because you have < and > characters inside your elements. They have to be escaped.

    If they were actually supposed to be comments, this is what it should be:

    <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<response>
<heartbeat><!--#exec cmd_argument='printf( "0x%02X%02X", InReadUByte( 0 ), InReadUByte( 1 ))'-->    </heartbeat>

<dmt node="1">
    <address><!--#exec cmd_argument='printf( "0x%02X", InReadUByte( 20 ))'--></address>
    <status><!--#exec cmd_argument='printf( "0x%02X", InReadUByte( 21 ))'--></status>
    <realflow><!--#exec cmd_argument='printf( "%f", InReadFloat( 22 ))'--></realflow>
    <pressure><!--#exec cmd_argument='printf( "0x%02X%02X", InReadUByte( 26 ), InReadUByte( 27 ))'--></pressure>
    <temp><!--#exec cmd_argument='printf( "0x%02X%02X", InReadUByte( 28 ), InReadUByte( 29 ))'--></temp>
</dmt>
</response>

    If that was actually supposed to be text, then they need to be escaped, like this:

    <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<response>
<heartbeat>&lt;?--#exec cmd_argument='printf( "0x%02X%02X", InReadUByte( 0 ), InReadUByte( 1 ))'--&gt;    </heartbeat>

<dmt node="1">
    <address>&lt;?--#exec cmd_argument='printf( "0x%02X", InReadUByte( 20 ))'--&gt;</address>
    <status>&lt;?--#exec cmd_argument='printf( "0x%02X", InReadUByte( 21 ))'--&gt;</status>
    <realflow>&lt;?--#exec cmd_argument='printf( "%f", InReadFloat( 22 ))'--&gt;</realflow>
    <pressure>&lt;?--#exec cmd_argument='printf( "0x%02X%02X", InReadUByte( 26 ), InReadUByte( 27 ))'--&gt;</pressure>
    <temp>&lt;?--#exec cmd_argument='printf( "0x%02X%02X", InReadUByte( 28 ), InReadUByte( 29 ))'--&gt;</temp>
</dmt>
</response>

    The above two documents are both valid.

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