用python ET解析xml，修改xml并保留标签前缀

# -*- coding: utf-8 -*-

import xml.etree.ElementTree as ET
ET.register_namespace("nms", "http://www.mycompany.com")
tree = ET.parse(r"test.xml")
root = tree.getroot()
print len(root)
id = 1
for document in root:
    print document.get('id')
    document.set('id', "%d"%(id))
    id = id + 1

tree.write(r"test.xml", encoding='utf-8', xml_declaration=True)

test.xml:

<?xml version='1.0' encoding='utf-8'?>
<nms:docset xmlns:nms="http://www.mycompany.com">
    <nms:document id="1">
        <content>text&lt;&gt;!@#$%^&amp;*()_-=+\/{}[] context haha</content>
    </nms:document>

    <nms:document id="2">
        <content>text&lt;&gt;!@#$%^&amp;*()_-=+\/{}[] context haha</content>
    </nms:document>

    <nms:document id="3">
        <content>text&lt;&gt;!@#$%^&amp;*()_-=+\/{}[] context haha</content>
    </nms:document>

    <nms:document id="4">
        <content>text&lt;&gt;!@#$%^&amp;*()_-=+\/{}[] context haha</content>
    </nms:document>

    <nms:document id="5">
        <content>text&lt;&gt;!@#$%^&amp;*()_-=+\/{}[] context haha</content>
    </nms:document>

    <nms:document id="6">
        <content>text&lt;&gt;!@#$%^&amp;*()_-=+\/{}[] context haha</content>
    </nms:document>

</nms:docset>

http://stackoverflow.com/questions/13372604/python-elementtree-parsing-unbound-prefix-error
http://stackoverflow.com/questions/4997848/emitting-namespace-specifications-with-elementtree-in-python