Python ElementTree module: How to ignore the namespace of XML files to locate matching element when using the method “find”, “findall”

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Question :

Python ElementTree module: How to ignore the namespace of XML files to locate matching element when using the method “find”, “findall”

I want to use the method of “findall” to locate some elements of the source xml file in the ElementTree module.

However, the source xml file (test.xml) has namespace. I truncate part of xml file as sample:

<?xml version="1.0" encoding="iso-8859-1"?>
<XML_HEADER xmlns="http://www.test.com">
    <TYPE>Updates</TYPE>
    <DATE>9/26/2012 10:30:34 AM</DATE>
    <COPYRIGHT_NOTICE>All Rights Reserved.</COPYRIGHT_NOTICE>
    <LICENSE>newlicense.htm</LICENSE>
    <DEAL_LEVEL>
        <PAID_OFF>N</PAID_OFF>
        </DEAL_LEVEL>
</XML_HEADER>

The sample python code is below:

from xml.etree import ElementTree as ET
tree = ET.parse(r"test.xml")
el1 = tree.findall("DEAL_LEVEL/PAID_OFF") # Return None
el2 = tree.findall("{http://www.test.com}DEAL_LEVEL/{http://www.test.com}PAID_OFF") # Return <Element '{http://www.test.com}DEAL_LEVEL/PAID_OFF' at 0xb78b90>

Although it can works, because there is a namespace “{http://www.test.com}”, it’s very inconvenient to add a namespace in front of each tag.

How can I ignore the namespace when using the method of “find”, “findall” and so on?

Answer #1:

Instead of modifying the XML document itself, it’s best to parse it and then modify the tags in the result. This way you can handle multiple namespaces and namespace aliases:

from io import StringIO  # for Python 2 import from StringIO instead
import xml.etree.ElementTree as ET

# instead of ET.fromstring(xml)
it = ET.iterparse(StringIO(xml))
for _, el in it:
    prefix, has_namespace, postfix = el.tag.partition('}')
    if has_namespace:
        el.tag = postfix  # strip all namespaces
root = it.root

This is based on the discussion here:
http://bugs.python.org/issue18304

Update: rpartition instead of partition makes sure you get the tag name in postfix even if there is no namespace. Thus you could condense it:

for _, el in it:
    _, _, el.tag = el.tag.rpartition('}') # strip ns
Answered By: nonagon

Answer #2:

If you remove the xmlns attribute from the xml before parsing it then there won’t be a namespace prepended to each tag in the tree.

import re

xmlstring = re.sub(' ]+"', '', xmlstring, count=1)
Answered By: user2212280

Answer #3:

The answers so far explicitely put the namespace value in the script. For a more generic solution, I would rather extract the namespace from the xml:

import re
def get_namespace(element):
  m = re.match('{.*}', element.tag)
  return m.group(0) if m else ''

And use it in find method:

namespace = get_namespace(tree.getroot())
print tree.find('./{0}parent/{0}version'.format(namespace)).text
Answered By: wimous

Answer #4:

Here’s an extension to nonagon’s answer, which also strips namespaces off attributes:

from StringIO import StringIO
import xml.etree.ElementTree as ET

# instead of ET.fromstring(xml)
it = ET.iterparse(StringIO(xml))
for _, el in it:
    if '}' in el.tag:
        el.tag = el.tag.split('}', 1)[1]  # strip all namespaces
    for at in list(el.attrib.keys()): # strip namespaces of attributes too
        if '}' in at:
            newat = at.split('}', 1)[1]
            el.attrib[newat] = el.attrib[at]
            del el.attrib[at]
root = it.root

UPDATE: added list() so the iterator works (needed for Python 3)

Answered By: barny

Answer #5:

Improving on the answer by ericspod:

Instead of changing the parse mode globally we can wrap this in an object supporting the with construct.

from xml.parsers import expat

class DisableXmlNamespaces:
    def __enter__(self):
            self.oldcreate = expat.ParserCreate
            expat.ParserCreate = lambda encoding, sep: self.oldcreate(encoding, None)
    def __exit__(self, type, value, traceback):
            expat.ParserCreate = self.oldcreate

This can then be used as follows

import xml.etree.ElementTree as ET
with DisableXmlNamespaces():
     tree = ET.parse("test.xml")

The beauty of this way is that it does not change any behaviour for unrelated code outside the with block. I ended up creating this after getting errors in unrelated libraries after using the version by ericspod which also happened to use expat.

Answered By: lijat

Answer #6:

You can use the elegant string formatting construct as well:

ns='http://www.test.com'
el2 = tree.findall("{%s}DEAL_LEVEL/{%s}PAID_OFF" %(ns,ns))

or, if you’re sure that PAID_OFF only appears in one level in tree:

el2 = tree.findall(".//{%s}PAID_OFF" % ns)
Answered By: tzp

Answer #7:

If you’re using ElementTree and not cElementTree you can force Expat to ignore namespace processing by replacing ParserCreate():

from xml.parsers import expat
oldcreate = expat.ParserCreate
expat.ParserCreate = lambda encoding, sep: oldcreate(encoding, None)

ElementTree tries to use Expat by calling ParserCreate() but provides no option to not provide a namespace separator string, the above code will cause it to be ignore but be warned this could break other things.

Answered By: ericspod

Answer #8:

I might be late for this but I dont think re.sub is a good solution.

However the rewrite xml.parsers.expat does not work for Python 3.x versions,

The main culprit is the xml/etree/ElementTree.py see bottom of the source code

# Import the C accelerators
try:
    # Element is going to be shadowed by the C implementation. We need to keep
    # the Python version of it accessible for some "creative" by external code
    # (see tests)
    _Element_Py = Element

    # Element, SubElement, ParseError, TreeBuilder, XMLParser
    from _elementtree import *
except ImportError:
    pass

Which is kinda sad.

The solution is to get rid of it first.

import _elementtree
try:
    del _elementtree.XMLParser
except AttributeError:
    # in case deleted twice
    pass
else:
    from xml.parsers import expat  # NOQA: F811
    oldcreate = expat.ParserCreate
    expat.ParserCreate = lambda encoding, sep: oldcreate(encoding, None)

Tested on Python 3.6.

Try try statement is useful in case somewhere in your code you reload or import a module twice you get some strange errors like

  • maximum recursion depth exceeded
  • AttributeError: XMLParser

btw damn the etree source code looks really messy.

Answered By: est

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