import re
import sys

if sys.version_info > (3, 0):
    def u(s):
        return s
else:
    def u(s):
        return unicode(s)

class _escape:
    def __init__(self):
        self.escape = {
            u('"') : u('&quot;'), u('<') : u('&lt;'), u('>') : u('&gt;'), 
            u('&') : u('&amp;'), u("'") : u('&apos;'),
            }
        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()