parse xml

[kostia]

I have xml file:
<?xml version="1.1" encoding="UTF-8"?>
<root>
        <n>50000</n>
</root>

I want to get the value of n (= 50000) inside my python program, I'm
doing this:

import xml.dom.minidom
from xml.dom.minidom import Node
doc = xml.dom.minidom.parseString("boolean_width.xml")
n = doc.getElementsByTagName("root")[0].firstChild.nodeValue.strip()
print n

and it is failed. How to get the value? Please, help.