Expand default (dita) attributes

My python libxml2 differently processes the files with the default attributes, depending on what I want to know what. The example, using the DITA DTD (the package can be downloaded on www.dita-ot.org):

import libxml2
import libxsltmod

s = """<!DOCTYPE map PUBLIC "-//OASIS//DTD XDITA Map//EN"
"file://.../dita-ot-2.2.1/plugins/org.oasis-open.dita.v1
_2/dtd/technicalContent/dtd/map.dtd">

<map title="Empty map">
</map>"""

libxml2.substituteEntitiesDefault(1)
xmldoc = libxml2.parseDoc(s)
print xmldoc

The output is as desired:

<?xml version="1.0"?>
<!DOCTYPE map PUBLIC "-//OASIS//DTD XDITA Map//EN"
"file://.../dita-ot-2.2.1/plugins/org.oasis-open.dita.v1
_2/dtd/technicalContent/dtd/map.dtd">
<map xmlns:ditaarch="http://dita.oasis-open.org/architecture/2005/"
  title="Empty map" ditaarch:DITAArchVersion="1.2" domains="(topic delay-d)
  (map mapgroup-d)                           (topic indexing-d)
  (map glossref-d)                          (topic hi-d)
  (topic ut-d)                           (topic hazard-d)
  (topic abbrev-d)                          (topic pr-d)
  (topic sw-d)                          (topic ui-d)
  " class="- map/map ">
</map>

But if I comment-out import libxsltmod, the result is:

<?xml version="1.0"?>
<!DOCTYPE map PUBLIC "-//OASIS//DTD XDITA Map//EN"
"file://.../dita-ot-2.2.1/plugins/org.oasis-open.dita.v
1_2/dtd/technicalContent/dtd/map.dtd">
<map title="Empty map">
</map>

So, libxsltmod makes something to activate default attributes expansion. Would you please suggest what, and how I can activate this functionality through python?

Solution

I have no idea how libxsltmod enables this setting globally, but normally, DTD default attributes are added with the parser option XML_PARSE_DTDATTR. Use readDoc instead of parseDoc to provide parser options:

xmldoc = libxml2.readDoc(s, None, None, libxml2.XML_PARSE_DTDATTR)

Or, if you also want to substitute entities:

flags = libxml2.XML_PARSE_NOENT | libxml2.XML_PARSE_DTDATTR
xmldoc = libxml2.readDoc(s, None, None, flags)