gae python ajax post

# MAIN.PY
# THIS IS THE FUNCTION URL FROM WHERE THE AJAX POST IS DONE:

template_dir = os.path.join(os.path.dirname(__file__), 'inc/html/')
jinja = jinja2.Environment(autoescape=True, loader=jinja2.FileSystemLoader(template_dir))

SETTINGS_PATH = os.path.normpath(os.path.dirname(__file__))
img_dir = os.path.join(SETTINGS_PATH, "inc/req")


class Test(webapp2.RequestHandler):
    def get(self):
        for file in os.listdir(img_dir):
            h = []
            h.append(file)
            for l in h:
                r = l.endswith('.jpg') or l.endswith('.png') or l.endswith('.gif')
                if r == True:
                    dd.append(l)
                    dd.sort()
        template_values = {'images': dd}
        template = jinja.get_template('img.html')               # The HTML file with AJAX.JS file
        self.response.write(template.render(template_values))

# THIS CLASS RECEIVES THE AJAX POST
class DoubleNumbers(webapp2.RequestHandler):
    def get(self):
        pass

    def post(self):
        self.response.headers['Content-Type'] = 'application/json'
        data = json.loads(self.request.body)
        z = data['imageSrc']
        logging.info(z)
    self.response.write(z)

app = webapp2.WSGIApplication([
        ('/tst', Test),             # AJAX POST from URL /tst to URL /i
    ('/i', DoubleNumbers),
], debug=True)

# THE JS FILE

$(document).ready(function() {
    $("button").click(function(){
        var data = {'imageSrc' : $(this).parent().find('img').attr('src')};

        var request = $.ajax({
            cache: false,
            url: "/i",
            type: "POST",
            data: JSON.stringify(data),
            dataType: "json",
        }).done(function(data){
        var txt = "<!DOCTYPE html><html><body><img src='"+data+"'></body></html>";
        document.open("text/html");
        document.write( txt );
        document.close();
        console.log(data);
        console.log(txt);
        });
    });
});