xmltodict

xmltodict is a Python module that makes working with XML feel like you are working with JSON, as in this "spec":

>>> print(json.dumps(xmltodict.parse("""
...  <mydocument has="an attribute">
...    <and>
...      <many>elements</many>
...      <many>more elements</many>
...    </and>
...    <plus a="complex">
...      element as well
...    </plus>
...  </mydocument>
...  """), indent=4))
{
    "mydocument": {
        "@has": "an attribute", 
        "and": {
            "many": [
                "elements", 
                "more elements"
            ]
        }, 
        "plus": {
            "@a": "complex", 
            "#text": "element as well"
        }
    }
}

Namespace support

By default, xmltodict does no XML namespace processing (it just treats namespace declarations as regular node attributes), but passing process_namespaces=True will make it expand namespaces for you:

>>> xml = """
... <root xmlns="http://defaultns.com/"
...       xmlns:a="http://a.com/"
...       xmlns:b="http://b.com/">
...   <x>1</x>
...   <a:y>2</a:y>
...   <b:z>3</b:z>
... </root>
... """
>>> xmltodict.parse(xml, process_namespaces=True) == {
...     'http://defaultns.com/:root': {
...         'http://defaultns.com/:x': '1',
...         'http://a.com/:y': '2',
...         'http://b.com/:z': '3',
...     }
... }
True

It also lets you collapse certain namespaces to shorthand prefixes, or skip them altogether:

>>> namespaces = {
...     'http://defaultns.com/': None, # skip this namespace
...     'http://a.com/': 'ns_a', # collapse "http://a.com/" -> "ns_a"
... }
>>> xmltodict.parse(xml, process_namespaces=True, namespaces=namespaces) == {
...     'root': {
...         'x': '1',
...         'ns_a:y': '2',
...         'http://b.com/:z': '3',
...     },
... }
True

Streaming mode

xmltodict is very fast (Expat-based) and has a streaming mode with a small memory footprint, suitable for big XML dumps like Discogs or Wikipedia:

>>> def handle_artist(_, artist):
...     print artist['name']
...     return True
>>> 
>>> xmltodict.parse(GzipFile('discogs_artists.xml.gz'),
...     item_depth=2, item_callback=handle_artist)
A Perfect Circle
Fantômas
King Crimson
Chris Potter
...

Also you can use generator, for this item_depth has to be greater than 0 and no item_callback. Since the generator uses a thread under the hood you need to use it from within a with statement so that the thread is correctly disposed of:

>>> with xmltodict.parse(GzipFile('discogs_artists.xml.gz'), item_depth=2) as gen:
...    artists_names = [artist['name'] for _, artist in gen]
... artists_names
['A Perfect Circle', 'Fantômas', 'King Crimson', 'Chris Potter']

It can also be used from the command line to pipe objects to a script like this:

import sys, marshal
while True:
    _, article = marshal.load(sys.stdin)
    print article['title']

$ cat enwiki-pages-articles.xml.bz2 | bunzip2 | xmltodict.py 2 | myscript.py
AccessibleComputing
Anarchism
AfghanistanHistory
AfghanistanGeography
AfghanistanPeople
AfghanistanCommunications
Autism
...

Or just cache the dicts so you don't have to parse that big XML file again. You do this only once:

$ cat enwiki-pages-articles.xml.bz2 | bunzip2 | xmltodict.py 2 | gzip > enwiki.dicts.gz

And you reuse the dicts with every script that needs them:

$ cat enwiki.dicts.gz | gunzip | script1.py
$ cat enwiki.dicts.gz | gunzip | script2.py
...

Roundtripping

You can also convert in the other direction, using the unparse() method:

>>> mydict = {
...     'response': {
...             'status': 'good',
...             'last_updated': '2014-02-16T23:10:12Z',
...     }
... }
>>> print unparse(mydict, pretty=True)
<?xml version="1.0" encoding="utf-8"?>
<response>
	<status>good</status>
	<last_updated>2014-02-16T23:10:12Z</last_updated>
</response>

Ok, how do I get it?

You just need to

$ pip install xmltodict

There is an official Fedora package for xmltodict. If you are on Fedora or RHEL, you can do:

$ sudo yum install python-xmltodict

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