xml的概念可以从html扩展进行理解
关键字:root, tag,element, attr
最后:XML parsing - ElementTree vs SAX and DOM
python解析xml的常用模块如下:
https://docs.python.org/2/library/xml.html#xml-vulnerabilities
import xml.dom.minidom
import xml.etree.ElementTree
import xml.sax
from lxml import etree