Sijax stands for "Simple ajax" and provides just that. It's a simple Python/jQuery library providing easy ajax integration for python web apps.
The main idea is to use javascript code that calls server-side callbacks, which generate a response (manipulating the DOM, etc) and pass it back to the client. This way, you don't need to manually dispatch ajax requests to certain URIs and go over each XML/JSON response manually.
Sijax was initially developed for PHP, inspired by the Xajax library (PHP-only).
Take a look at the documentation to learn more.