ToscaWidgets , in version 2, which is currently in the alpha test, is said to support App Engine (at least for tw2.corepart). I also saw posts showing ways (a bit complicated, it seemed to me) to use the current ToscaWidgets in the App Engine.
App Engine itself definitely doesn’t include such a widget package — it has WSGI (a much lower-level service that allows you to connect most of the Python web application frameworks of your choice), an extremely simple “webapp” request / response / router for simple applications , and django (in several versions - only 0.96 is part of the SDK download, but up to 1.1 for the actual service that I think), which uses templates, not widgets.
GAE , django (, , > 80% - Python ), , GAE (Python 2.5, , c). , werkzeug "non-framework", WSGI ( , , , Javascript , dojo/dijit Google Closure, jquery/jqueryUI - App Engine , , -).
, django mindshare ( Rails Ruby, ), Python - -, . Python 3 , Guido - , ... , , ! -)