[Django]-Simplest framework for converting python app into webapp?

Look at Bottle, great for simple webapps. Example code from their website:

from bottle import route, run

@route('/hello/:name')
def index(name='World'):
    return '<b>Hello %s!</b>' % name

run(host='localhost', port=8080)

CherryPy would serve you the best if you are looking for a minimalist one.

It small framework for webapp Flask framewrok

Maybe take a look at Google App Engine

+1 for bottle.

Nevertheless, consider that the scope usually grows when developing web apps and that text box and those 2 buttons will later on need: templates, lots of routes, maybe translations, etc. So, always consider using something that would allow you to move into some powerful framework such as web2py or Django.