template.html

<script type="text/javascript">

function compute() {
    var a = $('#value_a')[0].value;
    var b = $('#value_b')[0].value;
    $.ajax({
        url: '/compute/?a=' + a + '&b=' + b,
        success: function(data) {
            $('#result').html(data);
        }
    });
}

</script>


<p>
a = <input type="text" name="a" id="value_a"/>
b = <input type="text" name="b" id="value_b"/>
a + b = <span id="result">...</span>
<button onclick="compute()">compute</button>
</p>

views.py

from django.http import HttpResponse

def compute(request):
    a = int(request.GET['a'])
    b = int(request.GET['b'])
    c = a + b
    return HttpResponse('%d + %d = %d' % (a, b, c))