Define Default Namespace (unprefixed) In Lxml

January 27, 2023 Post a Comment

When rendering XHTML with lxml, everything is fine, unless you happen to use Firefox, which seems unable to deal with namespace-prefixed XHTML elements and javascript. While Opera

Solution 1:

Use ElementMaker and give it an nsmap that maps None to your default namespace.

#!/usr/bin/env python
# dogeml.py

from lxml.builder import ElementMaker
from lxml import etree

E = ElementMaker(
    nsmap={
        None: "http://wow/"    # <--- This is the special sauce
    }
)

doge = E.doge(
    E.such('markup'),
    E.many('very namespaced', syntax="tricks")
)

options = {
    'pretty_print': True,
    'xml_declaration': True,
    'encoding': 'UTF-8',
}

serialized_bytes = etree.tostring(doge, **options)
print(serialized_bytes.decode(options['encoding']))

As you can see in the output from this script, the default namespace is defined, but the tags do not have a prefix.

<?xml version='1.0' encoding='UTF-8'?>
<doge xmlns="http://wow/">
   <such>markup</such>
   <many syntax="tricks">very namespaced</many>
</doge>

I have tested this code with Python 2.7.6, 3.3.5, and 3.4.0, combined with lxml 3.3.1.

Solution 2:

This XSL transformation removes all prefixes from content, while maintaining namespaces defined in the root node:

import lxml.etree as ET

content = '''\
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE html>
<h:html xmlns:h="http://www.w3.org/1999/xhtml" xmlns:ml="http://foo">
  <h:head>
    <h:title>MathJax Test Page</h:title>
    <h:script type="text/javascript"><![CDATA[
      function test() {
        alert(document.getElementsByTagName("p").length);
      };
    ]]></h:script>
  </h:head>
  <h:body onload="test();">
    <h:p>test</h:p>
    <ml:foo></ml:foo>
  </h:body>
</h:html>
'''
dom = ET.fromstring(content)

xslt = '''\
<xsl:stylesheet version="1.0"
    xmlns="http://www.w3.org/1999/xhtml"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" indent="no"/>

<!-- identity transform for everything else -->
<xsl:template match="/|comment()|processing-instruction()|*|@*">
    <xsl:copy>
      <xsl:apply-templates />
    </xsl:copy>
</xsl:template>

<!-- remove NS from XHTML elements -->
<xsl:template match="*[namespace-uri() = 'http://www.w3.org/1999/xhtml']">
    <xsl:element name="{local-name()}">
      <xsl:apply-templates select="@*|node()" />
    </xsl:element>
</xsl:template>

<!-- remove NS from XHTML attributes -->
<xsl:template match="@*[namespace-uri() = 'http://www.w3.org/1999/xhtml']">
    <xsl:attribute name="{local-name()}">
      <xsl:value-of select="." />
    </xsl:attribute>
</xsl:template>
</xsl:stylesheet>
'''

xslt_doc = ET.fromstring(xslt)
transform = ET.XSLT(xslt_doc)
dom = transform(dom)

print(ET.tostring(dom, pretty_print = True, 
                  encoding = 'utf-8'))

yields

<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <title>MathJax Test Page</title>
    <script type="text/javascript">
      function test() {
        alert(document.getElementsByTagName("p").length);
      };
    </script>
  </head>
  <body onload="test();">
    <p>test</p>
    <ml:foo xmlns:ml="http://foo"/>
  </body>
</html>

Solution 3:

To expand on @neirbowj's answer, but using ET.Element and ET.SubElement, and rendering a document with a mix of namespaces, where the root happens to be explicitly namespaced and a subelement (channel) is the default namespace:

# I set up but don't use the default namespace:
root = ET.Element('{http://www.w3.org/1999/02/22-rdf-syntax-ns#}RDF', nsmap={None: 'http://purl.org/rss/1.0/'})
# I use the default namespace by including its URL in curly braces:
e = ET.SubElement(root, '{http://purl.org/rss/1.0/}channel')
print(ET.tostring(root, xml_declaration=True, encoding='utf8').decode())

This will print out the following:

<?xml version='1.0' encoding='utf8'?>
<rdf:RDF xmlns="http://purl.org/rss/1.0/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"><channel/></rdf:RDF>

It automatically uses rdf for the RDF namespace. I'm not sure how it figures it out. If I want to specify it I can add it to my nsmap in the root element:

nsmap = {None: 'http://purl.org/rss/1.0/',
         'doge': 'http://www.w3.org/1999/02/22-rdf-syntax-ns#'}
root = ET.Element('{http://www.w3.org/1999/02/22-rdf-syntax-ns#}RDF', nsmap=nsmap)
e = ET.SubElement(root, '{http://purl.org/rss/1.0/}channel')
print(ET.tostring(root, xml_declaration=True, encoding='utf8').decode())

...and I get this:

<?xml version='1.0' encoding='utf8'?>
<doge:RDF xmlns:doge="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns="http://purl.org/rss/1.0/"><channel/></doge:RDF>

Python Development

Define Default Namespace (unprefixed) In Lxml

Solution 1:

Solution 2:

Solution 3:

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