lxml RangedTarget for hacking in ranged sourceline numbers

RangedTarget.py

from lxml import etree

class RangedTarget(etree.TreeBuilder):
    """
    Extends the regular etree.TreeBuilder target to assign all elements
    built two attributes:
        ranged_tag_start = line number of the start tag
        ranged_tag_end = line number of the end tag

    To use this, you must feed the parser line by line, while assigning
    the current line number to this object.

    Example use:

        with open('test.xml') as f:
            lines = f.readlines()

        parser = etree.XMLParser(target=RangedTarget())
        for i in range(len(lines)):
            parser.target.current_line = i
            parser.feed(lines[i])

        root = parser.close()

        for event, element in etree.iterwalk(root):
                print("%s, %s, %s" % (event, element.tag, element.attrib))

    """

    def __init__(self, element_factory=None, parser=None):
        super(RangedTarget, self).__init__(element_factory=element_factory,
                parser=parser)

        self.current_line = None

    @property
    def current_line(self):
        return self._line

    @current_line.setter
    def current_line(self, line):
        self._line = line

    def end(self, tag):
        element = super(RangedTarget, self).end(tag)
        element.set('ranged_tag_start', str(element.sourceline))
        element.set('ranged_tag_end', str(self.current_line))
        return element