"""
This module monkey patches the ElementTree module to fully support CDATA
sections both while generating XML trees and while parsing XML documents.
See usage examples at the end of this file.
Eli Golovinsky, 2008
www.gooli.org
"""
try:
# Try Python 2.5 and later
import xml.etree.ElementTree as etree
except ImportError:
# Older Python with ElementTree installed from http://effbot.org/zone/element-index.htm
import elementtree.ElementTree as etree
def CDATA(text=None):
"""
A CDATA element factory function that uses the function itself as the tag
(based on the Comment factory function in the ElementTree implementation).
"""
element = etree.Element(CDATA)
element.text = text
return element
# We're replacing the _write method of the ElementTree class so that it would
# recognize and correctly print out CDATA sections.
old_ElementTree = etree.ElementTree
class ElementTree_CDATA(old_ElementTree):
def _write(self, file, node, encoding, namespaces):
if node.tag is CDATA:
if node.text:
text = node.text.encode(encoding)
file.write("<![CDATA[%s]]>" % text)
else:
old_ElementTree._write(self, file, node, encoding, namespaces)
etree.ElementTree = ElementTree_CDATA
# Since xml.parsers.expat supports parsing CDATA sections, all we need to do
# is recognize them during parsing and add them to the tree.
old_XMLTreeBuilder = etree.XMLTreeBuilder
class XMLTreeBuilder_CDATA(old_XMLTreeBuilder):
def __init__(self, html=0, target=None):
old_XMLTreeBuilder.__init__(self, html, target)
self._parser.StartCdataSectionHandler = self._start_cdata
self._parser.EndCdataSectionHandler = self._end_cdata
self._cdataSection = False
self._cdataBuffer = None
def _start_cdata(self):
"""
A CDATA section beginning has been recognized - start collecting
character data.
"""
self._cdataSection = True
self._cdataBuffer = []
def _end_cdata(self):
"""
The CDATA section has ended - join the character data we collected
and add a CDATA element to the target tree.
"""
self._cdataSection = False
text = self._fixtext("".join(self._cdataBuffer))
self._target.start(CDATA, {})
self._target.data(text)
self._target.end(CDATA)
def _data(self, text):
"""
If we are in the middle of a CDATA section, collect the data into a
special buffer, otherwise treat it as before.
"""
if self._cdataSection:
self._cdataBuffer.append(text)
else:
old_XMLTreeBuilder._data(self, text)
etree.XMLTreeBuilder = XMLTreeBuilder_CDATA
try:
# Try Python 2.5 and later
from xml.etree.ElementTree import *
except ImportError:
# Older Python with ElementTree installed from http://effbot.org/zone/element-index.htm
from elementtree.ElementTree import *
# ------------------------------------------------------------------------------
if __name__ == "__main__":
sampleXml = '<data key="value"> some text <![CDATA[<sender>John Smith</sender>]]></data>'
# Parse XML that contains CDATA sections and convert it back into a string
root = fromstring(sampleXml)
xml = tostring(root)
print xml
# The parsed and regenerated XML is the same as the sample XML string
assert(sampleXml == xml)
# Generate a tree with a CDATA section
root = Element("data")
root.set("key", "value")
root.text = " some text "
cdata = CDATA("<sender>John Smith</sender>")
root.append(cdata)
xml2 = tostring(root)
print xml2
# The generated XML is the same as the sample XML string
assert(sampleXml == xml2)
