import re

class _escape:

    def __init__(self):

        self.escape = {

            u'"' : u'&quot;', u'<' : u'&lt;', u'>' : u'&gt;', 

            u'&' : u'&', u"'" : u''',

            }

        self.charef_rex = re.compile(u"|".join(self.escape.keys()))

    def _replacer(self, match):

        return self.escape[match.group(0)]

    def __call__(self, ustring):

        """ xml-escape the given unicode string. """

        return self.charef_rex.sub(self._replacer, ustring)

escape = _escape()