Python: namespaces in xml ElementTree (or lxml)

I want to retrieve a legacy xml file, manipulate and save it.

Here is my code:

from xml.etree import cElementTree as ET
NS = "{http://www.somedomain.com/XI/Traffic/10}"

def fix_xml(filename):
    f = ET.parse(filename)
    root = f.getroot()
    eventlist = root.findall("%(ns)Event" % {'ns':NS })
    xpath = "%(ns)sEventDetail/%(ns)sEventDescription" % {'ns':NS }
    for event in eventlist:
        desc = event.find(xpath)
        desc.text = desc.text.upper() # do some editting to the text.

    ET.ElementTree(root, nsmap=NS).write("out.xml", encoding="utf-8")


shorten_xml("test.xml")

The file I load contains:

xmlns="http://www.somedomain.com/XI/Traffic/10"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.somedomain.com/XI/Traffic/10 10.xds"

at the root tag.

I have the following problems, related to namespace:

• As you see, for each tag call, I have give the namespace at the begining to retreive a child.
• Generated xml file doesn't have at the begining.
• The tags at the output contains such while I need output as the original , without namespace at the begining.

How can these be solved?