Accessing XMLNS attribute with Python Elementree?

Question

How can one access NS attributes through using ElementTree?

With the following:

<data xmlns="http://www.foo.net/a" xmlns:a="http://www.foo.net/a" book="1" category="ABS" date="2009-12-22">

When I try to root.get('xmlns') I get back None, Category and Date are fine, Any help appreciated..

Answer 1

I think element.tag is what you're looking for. Note that your example is missing a trailing slash, so it's unbalanced and won't parse. I've added one in my example.

>>> from xml.etree import ElementTree as ET
>>> data = '''<data xmlns="http://www.foo.net/a"
...                 xmlns:a="http://www.foo.net/a"
...                 book="1" category="ABS" date="2009-12-22"/>'''
>>> element = ET.fromstring(data)
>>> element
<Element {http://www.foo.net/a}data at 1013b74d0>
>>> element.tag
'{http://www.foo.net/a}data'
>>> element.attrib
{'category': 'ABS', 'date': '2009-12-22', 'book': '1'}

If you just want to know the xmlns URI, you can split it out with a function like:

def tag_uri_and_name(elem):
    if elem.tag[0] == "{":
        uri, ignore, tag = elem.tag[1:].partition("}")
    else:
        uri = None
        tag = elem.tag
    return uri, tag

For much more on namespaces and qualified names in ElementTree, see effbot's examples.

Answer 2

Look at the effbot namespaces documentation/examples; specifically the parse_map function. It shows you how to add an *ns_map* attribute to each element which contains the prefix/URI mapping that applies to that specific element.

However, that adds the ns_map attribute to all the elements. For my needs, I found I wanted a global map of all the namespaces used to make element look up easier and not hardcoded.

Here's what I came up with:

import elementtree.ElementTree as ET

def parse_and_get_ns(file):
    events = "start", "start-ns"
    root = None
    ns = {}
    for event, elem in ET.iterparse(file, events):
        if event == "start-ns":
            if elem[0] in ns and ns[elem[0]] != elem[1]:
                # NOTE: It is perfectly valid to have the same prefix refer
                #     to different URI namespaces in different parts of the
                #     document. This exception serves as a reminder that this
                #     solution is not robust.    Use at your own peril.
                raise KeyError("Duplicate prefix with different URI found.")
            ns[elem[0]] = "{%s}" % elem[1]
        elif event == "start":
            if root is None:
                root = elem
    return ET.ElementTree(root), ns

With this you can parse an xml file and obtain a dict with the namespace mappings. So, if you have an xml file like the following ("my.xml"):

<?xml version="1.0" encoding="UTF-8" ?>
<rss version="2.0"
xmlns:content="http://purl.org/rss/1.0/modules/content/"
xmlns:dc="http://purl.org/dc/elements/1.1/"\
>
<feed>
  <item>
    <title>Foo</title>
    <dc:creator>Joe McGroin</dc:creator>
    <description>etc...</description>
  </item>
</feed>
</rss>

You will be able to use the xml namepaces and get info for elements like dc:creator:

>>> tree, ns = parse_and_get_ns("my.xml")
>>> ns
{u'content': '{http://purl.org/rss/1.0/modules/content/}',
u'dc': '{http://purl.org/dc/elements/1.1/}'}
>>> item = tree.find("/feed/item")
>>> item.findtext(ns['dc']+"creator")
'Joe McGroin'

Answer 3

Try this:

import xml.etree.ElementTree as ET
import re
import sys

with open(sys.argv[1]) as f:
    root = ET.fromstring(f.read())
    xmlns = ''
    m = re.search('{.*}', root.tag)
    if m:
        xmlns = m.group(0)
    print(root.find(xmlns + 'the_tag_you_want').text)