Q:

How do I validate xml against a DTD file in Python

I need to validate an XML string (and not a file)
against a DTD description file.  
How can that be done in python? 

A:

Another good option is lxml's validation which I find quite pleasant to use. 
A simple example taken from the lxml site:
from StringIO import StringIO

from lxml import etree

dtd = etree. DTD(StringIO("""<!ELEMENT foo EMPTY>"""))
root = etree. XML("<foo/>")
print(dtd.validate(root))
# True

root = etree. XML("<foo>bar</foo>")
print(dtd.validate(root))
# False
print(dtd.error_log.filter_from_errors())
# <string>:1:0:ERROR:VALID:DTD_NOT_EMPTY: Element foo was declared EMPTY this one has content

A:

from the examples directory in the libxml2 python bindings:
#! /usr/bin/python -u
import libxml2
import sys

# Memory debug specific
libxml2.debugMemory(1)

dtd="""<!ELEMENT foo EMPTY>"""
instance="""<?xml version="1.0"? >
<foo></foo>"""

dtd = libxml2.parseDTD(None, 'test.dtd')
ctxt = libxml2.newValidCtxt()
doc = libxml2.parseDoc(instance)
ret = doc.validateDtd(ctxt, dtd)
if ret ! = 1:
    print "error doing DTD validation"
    sys.exit(1)

doc.freeDoc()
dtd.freeDtd()
del dtd
del ctxt

