[XML-SIG] Bug in expatreader module...

[Achim Gaedke]

(This is the same topic as in comp.lang.python)

Hello everybody!

My intention is to write a recursive parser for nested data structures.
In order to collect the data it is necessary to switch the
contenthandler each step.

This does NOT work for the character handler: This is my (lean) test
program:

import xml.sax.handler

parser=3Dxml.sax.make_parser()

class second_ch(xml.sax.handler.ContentHandler):
    def startElement(self,name,attrs):
        print "start second"

    def endElement(self,name):
        print "end second"

    def characters(self,content):
        print "second: ",content.strip()

class first_ch(xml.sax.handler.ContentHandler):
    def startElement(self,name,attrs):
        print "start first"
        self.second=3Dsecond_ch()
        parser.setContentHandler(self.second)

    def endElement(self,name):
        print "end first"

    def characters(self,content):
        print "first: ",content.strip()

first=3Dfirst_ch()
parser.setContentHandler(first)
parser.parse('members.xml')

and this is the xml file members.xml:
<?xml version=3D"1.0"?>
<a>a1<b>b1</b>a2</a>

more is not necessary. This is the output with python2.0 and
expat-1.95.2


python2.0 xml_test.py
start first
first:  a1
start second
first:  b1
end second
first:  a2
end second

After the first line the second content handler should get the
characters!

The second test is with python2.1 and expat1_1:
python2.1 xml_test.py
start first
first:  a1
start second
first:  b1
end second
first:  a2
end second

the result is the same. What a pity.
In expat reference it is stated, that changing of handler is possible
and
expected.

I am running Redhat Linux 7.1 with self built python interpreters.

Ok, here is a workaround, I found in order to go on coding:

Add the following line after each

   parser.setContenHandler(new_handler)

for the missing functionality of parser.setContentHandler():

   parser._parser.CharacterDataHandler=3Dnew_handler.characters

This line is taken from xml.sax.expatreader.ExpatReader.reset()
This does work after parser.reset() or after parser.parse(...)  is
called once (because parse() calls reset()).

I think this error should be corrected somewhere else and not in my
code, but I don't know where and I hope that I will address maintainers
here, too.

Please let me know when this bug is fixed.

Yours

Achim

--
Achim Gaedke, ZPR
Weyertal 80, 50931 K=F6ln
Tel: +49 221 470 6021