OpenRico_ is a Javascript for Rich Application library including ajax, drag&drop and many visual effects.
Here explains ajax servlet with OpenRico. 

The Ajax Servlet library AjaxServlet.py::

    from WebKit.RPCServlet import RPCServlet

    class AjaxServlet(RPCServlet):
        def awake(self, transaction):
            RPCServlet.awake(self, transaction)
            self._response = transaction.response()
            self._request = transaction.request()

            self._session = transaction.session()
            self._resp = []
        def sleep(self, transaction):
            RPCServlet.sleep(self, transaction)
            self._response = None
            self._request = None
            self._session = None
            self._resp = None

        def respondToGet(self, trans):
            try:
                # ajax servlet don't need cache
                resp = self.response()
                resp.setHeader('Cache-Control', 'no-cache')
                resp.setHeader('Pragma', 'no-cache');

                self.writeln('<ajax-response>')
                self._respond()
                self.writeln('</response></ajax-response>')

                self.sendOK('text/xml', ''.join(self._resp), trans)
            finally:
                pass # do error handling or database release

        def request(self): return self._request
        def response(self): return self._response
        def transaction(self): return self._transaction

        def _respond(self):
            """ Here goes the response
            self.write('<span>Here is ajax response!!</span>')

            NOTE: You must call responseToElement() or responseToObject() before write something
            """
            raise NotImplementedError


        def responseToElement(self, elementId):
            self.write('<response type="element" id="%s">' % elementId)

        def responseToObject(self, objectId):
            self.write('<response type="object" id="%s">' % objectId)

        def write(self, *args):
            for arg in args:
                self._resp.append(self.encode(str(arg)))

        def writeln(self, *args):
            self.write(*args)
            self.write("\n")

        def decode(self, str, encoding='euc-kr'):
            """ Decode JavaScript quoted string to native string """
            ret = []

            while s:
                if s[:2].lower() == '%u':   # 유니코드 인코딩
                    char = s[:6]
                    unicode_chr = int( char[2:], 16)
                    try: ret.append( unichr(unicode_chr).encode(encoding) )
                    except UnicodeEncodeError: ret.append( '&#%s;' % unicode_chr )
                    s = s[6:]
                else:
                    ret.append( s[0] )
                    s = s[1:]

            return ''.join(ret)


        def encode(self, str, encoding='euc-kr'):
            """ Encode string to HTML unicode representation """
            p = string.printable
            ret = []
            for c in unicode(str, encoding):
                if c in p: ret.append(c)
                else: ret.append( '&#%d;' % ord(c) )
            return ''.join(ret)


search zipcode servlet example:::

    from AjaxServlet import *
    from Zipcode import *

    class ajax_search_zipcode(AjaxServlet):
        def _respond(self):
            self.responseToElement('search_result')
            zipcode_list = Zipcode.search(self.decode(self.request().field('dong')))

            self.write("""<table cellspacing="1" cellpadding="1" width="100%" bgcolor="black" bordercolordark="#DDDDDD" bordercolorlight="#666666">
       <tr align="center" bgcolor="#DDDDDD" height="22">
           <td bgcolor="#DDDDDD">우편번호</td>
           <td bgcolor="#DDDDDD">주 소</td>
           <td bgcolor="#DDDDDD">선택</td>
       </tr>\n""")

            for z in zipcode_list:
                self.write( """<tr bgcolor="#DDDDDD">
        <td bgcolor="#FFFFFF" style="white-space: nowrap;">%s</td>
        <td bgcolor="#FFFFFF" style="white-space: nowrap;">%s %s %s %s</td>
        <td bgcolor="#FFFFFF"><input type="button" value="선택" onClick="postaddr('%s', '%s');"/></td>
    </tr>\n""" % ( z[0], z[1], z[2], z[3], z[4], z[0], z[1] + z[2] + z[3] ) )
            self.write('</table>')

for real working example:

1. goto http://www.bodd.co.kr/member_register (only korean site)
2. click |image| button.
3. input "신림9" and click first button

.. |image| image:: http://www.bodd.co.kr/image/btn_zipcodesearch.jpg

-- whitekid_