Print output to webpage Django

Question

I currently have a long running script which produces various output. What I want to do is have this script run when a button on my webapp is pressed, and for the output to be displayed in real time in a text area on the webpage. I was wondering the simplest way to achieve this using Django.

Take a look: http://stackoverflow.com/questions/4787530/does-django-have-a-way-to-open-a-http-long-poll-connection — alecxe, Mar 03 '14 at 17:24
There is no extremely simple way to do this, so you'll probably get several totally different answers that are all solutions to different, more specific problems. More info about your requirements (how close to real time do you need it? Do you expect constant streaming output or just occasional output that you want displayed immediately? etc) would help — Andrew Gorcester, Mar 03 '14 at 21:35

score 3 · Answer 1 · answered Mar 03 '14 at 18:01

If you are talking about real time output then you need to use AJAX.

To set off the script, in the webpage you can have a button that sends an AJAX request.

function ajax_call_model(data_JSON_Request, object_id){
    $(function jQuery_AJAX_model(){
        $.ajax({
          type: 'GET',
          url: '/ajax_request/',
          data: something,
          datatype: "json",
          success: function(data) {
            $("#output_id").html(data);
          },//success
          error: function() {alert("failed...");}
        });//.ajax
      });//jQuery_AJAX
    };//ajax_call

In views you will have something like this:

def ajax_request(request):
    something = request.GET.get('something', '')# Receives from AJAX
    output = #Does something with the request
    jsonDump = json.dumps(str(output))

    return HttpResponse(jsonDump, content_type='application/json')

score 2 · Accepted Answer · answered Mar 03 '14 at 21:26

What you need is a WebSocket! Not supported directly by django, but I would recommend taking a look at Websockets for Django applications using Redis. I have used this before and it is really easy to set up and use.

For example create a django template (e.g. output.html):

<html>
...
<body>
  <textarea id="output" row=3 cols=25></textarea>

  <script>
    var ws = new WebSocket('{{ ws_url }}');
    ws.onmessage = function(e) {
      $('#output').append(e.data); 
    };
  </script>
</body>
</html>

Then create a method which your script calls whenever it wants to output a message to the text area:

def output_message(session_key, user, message):
    conn = redis.StrictRedis()
    ws_url = '{0}:{1}'.format(session_key, user)
    conn.publish(ws_url, message)

And finally you need to specify in your views.py a method which renders your output.html template:

def output_console(request):
    template_values = {'ws_url':'ws://{SERVER_NAME}:{SERVER_PORT}/ws/{0}?subscribe-session'.format(request.user.id, **request.META)}
    return render(request, 'output.html', template_values)

Take a look at the chat server on the projects git repo for a more in-depth code example.

Hope that helps, and best of luck!

Print output to webpage Django

2 Answers2