from lxml import etree as ET

xmlString = """
    <some_root_name>
        <tag_x>bubbles</tag_x>
        <tag_y>car</tag_y>
        <tag...>42</tag...>
    </some_root_name> """

document = ET.fromstring(xmlString)
for elementtag in document.getiterator():
   print "elementtag name:", elementtag.tag

编辑：
要从文件中读取而不是从字符串中读取

To read from file instead of from string

document = ET.parse("myxmlfile.xml")