Assuming you already know how to write a view in Flask
that responds to a url, create one that reads the request.post
data. To add the input box
to this post data create a form on your page with the text box. You can then use jquery
to do
var data = $('#<form-id>').serialize()
and then post to your view asynchronously using something like the below.
$.post('<your view url>', function(data) {
$('.result').html(data);
});