import xml.etree.ElementTree as ET

class XmlParser:
    def __init__(self):
        self.pm = self

    def display(self, result): pass

    def parseXml(self, dict, name):
        for event, elem in ET.iterparse(name, events=('start', 'end')):
            try:
                try: self.display(apply( dict[elem.tag], [self, event == 'start', elem]))
                except Exception, e:
                    print '\nevent error (%s): %s[%s]' % (e, elem.tag, event)
                    return
            except Exception, e: print '\nunhandled exception (%s):  %s[%s]' % (e, elem.tag, event)
        return self


class TestFile(XmlParser):
    def __init__(self, name):
        XmlParser.__init__(self)
        self.name = name
        self.x = 0

    def parse(self):
        self.parseXml(TestFile.__dict__, self.name)

    def a(self, ev, elem):
        pass

    def b(self, ev, elem):
        if ev != None:
            if elem.text == None: raise Exception((self.x, ev, elem))
            self.x = self.x + 1

xml = TestFile('test.xml')
xml.parse()