SwampDragon push notification

Push notification, one of the complex problem that a occurs for a web developer. Old time we need to install number of packages and make numerous changes in django files especially wsgi.py file to make it work. But now we have SwampDragon to help us out. SwampDragon made push notification too easy (not that easy...) implement compared to former method.

SwampDragon

SwampDragon helps to create near real-time functionality for Django via web socket support.Swamp dragon consists of:

• Redis. Basically a very quick, persistent kind of memcache. Supports pubsub.
• Tornado. A python webserver. Non-blocking IO. Lots of connections are no problem.
• Django.

Below I shown the simple work flow using swampdragon and django:
 

How To 

 

Below I have explained how to send notification to one or more users using same channel with the help of swamdragon and django.

Hope that you have already created your django app.

After that install the following packages:

To install SwampDragon:

 
pip install swampdragon

or

pip install -e git://github.com/jonashagstedt/swampdragon.git#egg=swampdragon

Install redis server (If you don't have redis)

 
sudo apt-get install redis-server

After installation redis server will start automatically. If not use the following command

 
sudo service redis-server start

Now redis server will be up and running. In settings.py file add swampdragon to installed app.
Also add SWAMP_DRAGON_CONNECTION and DRAGON_URL.

 
INSTALLED_APPS = (
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'swampdragon',
) 
SWAMP_DRAGON_CONNECTION = ('swampdragon.connections.sockjs_connection.DjangoSubscriberConnection', '/data')

DRAGON_URL = 'http://localhost:9999/'

Create router.py file in the app folder. Router.py helps in routing incoming connection to specified endpoint. 

 
from swampdragon import route_handler
from swampdragon.route_handler import BaseRouter

class MyRouter(BaseRouter):
    route_name = 'my-route'
    valid_verbs = [ 'subscribe']

    def get_subscription_channels(self, **kwargs):
        return ['notification']

route_handler.register(MyRouter)

Now create a js file. Let it be router.js .
Add the channel subscription and all display method for incoming message, inside the router.js file.

 
swampdragon.ready(function () {
//subscribes the channel and router
    swampdragon.subscribe('my-route', 'notification', null, function (context, data) {
        // any thing that happens after successfully subscribing
    }, function (context, data) {
        // any thing that happens if subscribing failed
    });
});
//Extracts message in the channel
swampdragon.onChannelMessage(function (channel, data) {
            InsertMsg2Html( data.data.message);
});

//inserts the received message from the channel to html 
function InsertMsg2Html(msg) {
    var messages = document.getElementById("notification");

    var span = document.createElement("span");
    messages.insertBefore(span, notification.firstChild);
    div.innerHTML = "<strong>" + msg + "</strong> " ;
}

In your template add the following lines:

    <script type="text/javascript" src="http://localhost:9999/settings.js"></script>
    <script type="text/javascript" src="js/sockjs-0.3.4.min.js"></script>
    <script type="text/javascript" src="js/swampdragon.js"></script>
    <script type="text/javascript" src="/js/router.js"></script>
    <script type="text/javascript" src="js/datamapper.js"></script>
    <script type="text/javascript" src="js/services.js"></script>

Now in views.py 

from swampdragon.pubsub_providers.data_publisher import publish_data

data = { 'message': 'You have successfully send a request'}
publish_data(channel='notification', data=data)

Here publish_data method will publish the data to the specified channel. onChannelMessage mentioned in the router.js gets the published message. Remaining logic to what to do with the incoming message can be changed depending up on the user requirement.

Django Profiler

Recently I have used many profilers in python which got me thinking about using profiler in a django app. So I started searching for ways to use a profiler in django. I have tried integrating many python profiler in django app's views.py file but it didn't go well as I expected. But then I tried to remove the profile added in the py file and used python's builtin profiler cProfile. I used the following command to execute python profiler along with the django runserver.

 
   $ python -m cProfile manage.py runserver

At first I couldn't figure out the way to get the profiler output while running the django dev server. As soon as I terminate the server the profiler output began to display in the terminal. Yes I got an output from profile but not the expected way. The present generated profiler output was the profiler output of the all the django process from the beginning of the server starting which is not easy to go through especially the list was too long. So I continued the R&D and finally reached at a py file which is added as a middleware file in django. Way the profiler work is like this after starting the server you can access the profiler data by typing ?prof which will open the profiler output of the current page in the browser. The profiler code is mentioned below.

 
try:
    import cProfile as profile
except ImportError:
    import profile

try:
    from cStringIO import StringIO
except:
    from io import StringIO

import pstats
from django.conf import settings


class ProfilerMiddleware(object):
    """
    Simple profile middleware to profile django views. To run it, add ?prof to
    the URL like this:

        http://localhost:8000/view/?prof

    Optionally pass the following to modify the output:

    ?sort => Sort the output by a given metric. Default is time.
        See http://docs.python.org/2/library/profile.html#pstats.Stats.sort_stats
        for all sort options.

    ?count => The number of rows to display. Default is 100.

    This is adapted from an example found here:
    http://www.slideshare.net/zeeg/django-con-high-performance-django-presentation.
    """
    def can(self, request):
        return settings.DEBUG and 'prof' in request.GET and \
            request.user is not None and request.user.is_staff

    def process_view(self, request, callback, callback_args, callback_kwargs):
        if self.can(request):
            self.profiler = profile.Profile()
            args = (request,) + callback_args
            try:
                return self.profiler.runcall(callback, *args, **callback_kwargs)
            except:
                # we want the process_exception middleware to fire
                # https://code.djangoproject.com/ticket/12250
                return

    def process_response(self, request, response):
        if self.can(request):
            self.profiler.create_stats()
            io = StringIO()
            stats = pstats.Stats(self.profiler, stream=io)
            stats.strip_dirs().sort_stats(request.GET.get('sort', 'time'))
            stats.print_stats(int(request.GET.get('count', 100)))
            response.content = '<pre>%s</pre>' % io.getvalue()
        return response

Steps:

• Copy paste the code to file and save it as .py file.
• Add the file to the MIDDLEWARE_CLASSES section in djnago settings.py file.
• Run the django server.
• To see the profiler add '?prof' after the url in the browser. (eg: http://12.0.0.1:8000/home/?prof )

For other profilers for django app:
     Profiling Django
     Django Live Profiler

Python Profilers

Code optimization is one of the obstacles that every developer now a days come across. There are lot of tools present now a days to optimize code. You can find python builtin or 3rd party modules for code optimization. Below I have mentioned a few codes optimization tools that I have used.

Builtin Modules

• Profile

  
  
  How To :  First of all import profile into you python code. Then at the main method use the profile.run() method. On executing the py file we will provide the profiler output. An example code is shown below:
  
  

   
  import profile
  
  
  def add(first, second):
      return first + second
  
  
  profile.run(' print add(1,2); print ')
  
  
  

        Profile module also provides runtx( ) for custom profiler generation.
  

• cProfile

  
  
  How To :This module can be used in two ways. One is to import the module and call it as cProfile.run( <your method> )Second is to call the cProfile module at the time of file execution.
  
  

    
     python -m cProfile pythonfile.py
  
  

• pstat

  
  
  How To: Standard report produced by the profile module is not very flexible. So depending upon the need the user can save the output of the run() or runtx() and process it using the Stats class from pstat.

Third Party Modules

• Line Profiler

  
         How To :  First of all install line profile using the following command.
  

   
     pip install line_profiler
  
  

  Then add the @profile above your method definition. Finally execute the code using the following command.

  
    $ kernprof.py -l -v fib.py
  
  

  
  

Converting rml file to pdf

PDF generation using reportlab's rml file

What is RML?
RML is the Report Markup Language - a member of the XML family of languages, and the XML dialect used by rml2pdf to produce documents in Adobe's Portable Document Format (PDF).RML documents can be written automatically by a program or manually using any word processor that can output text files (e.g. using a "Save as Text" option from the save menu). Since RML documents are basic text files, they can be created on the fly by scripts in Python, Perl, or almost any other language. RML makes creating documents in PDF as simple as creating a basic web page - RML is as easy to write as HTML, and uses "tags" just like HTML. It is much easier than trying to write PDF programmatically.
User guide for rml can be found here.


Installation:
 You will have to download and install reportlab plus. You can find the installation steps here.


(Assuming that you have already created a django app)

Now consider the case that I have an xml file which I need to convert to pdf. For that first you will have to create an rml file depending upon your need and save with .rml extension.

RML sample files can be found here.

In views.py import the required modules.

from rlextra.rml2pdf import rml2pdf
import xml.etree.ElementTree as ElementTree
from xml.dom import minidom

Next we write a function to obtain the rml file. The function at first extracts data from the xml file (as dict) the pass it on to the rml through context. Finally the function returns an rml in the specified encoded format  .

def getRML():
    xmldict = {}
    tree = ElementTree.parse('path to your xml file')
    root = tree.getroot()
    xmldict = XmlDictConfig(root)
    t = Template(open('path your rml file').read())
    c = Context({"xmldata": xmldict}) 
    rml = t.render(c)
    #django templates are unicode, and so need to be encoded to utf-8
    return rml.encode('utf16')

Last step is the pdf generation process.

class ConvertView(View):
   

    def get(self, request, *args, **kwargs):
        rml = getRML()
        buf = cStringIO.StringIO()
        
        #create the pdf
        rml2pdf.go(rml, outputFileName='output.pdf')
        buf.reset()
        pdfData = buf.read()
        
        #send the response
        response = HttpResponse(mimetype='application/pdf')
        response.write(pdfData)
        response['Content-Disposition'] = 'attachment; filename=output.pdf'
        return response

Now in urls.py :

from app.views import ConvertView

urlpatterns = patterns('',
    url(r'^admin/', include(admin.site.urls)),
    url(r'^convert/$', ConvertView.as_view(), name="convert2pdf"),
      
)

Finally call the 'convert' url to obtain the pdf document.

PDF generation using easy pdf

 

PDF generation using easy pdf

Easy pdf is a pdf rendering django package. You can install it with the following command:

$ pip install django-easy-pdf
$ pip install "xhtml2pdf>=0.0.6" "reportlab>=2.7,<3"
 

Easy pdf documentation can be found here

Now in your views.py file:

import easy_pdf
from easy_pdf.views import PDFTemplateView 



class MyView(PDFTemplateView):
     template_name = "converter.html"
     pdf_filename = "Output.pdf"


    def post(self, request, args, kwargs):
          objects = MyReport.objects.all()           
          context = { 'objects'  : objects}
          return  easy_pdf.rendering.render_to_pdf_response(request,  self.template_name, context, filename='Output.pdf', encoding=u'utf-8', **kwargs)

Now in urls.py :

from app.views import MyView

urlpatterns = patterns('',
    url(r'^admin/', include(admin.site.urls)),
    url(r'^convert/$', MyView.as_view(), name="convert2pdf"),
      
)

Finally call the 'convert' url to obtain the pdf document.

PDF generation using jspdf

Python and PDF generation

PDF generation using python is one of the trickiest task that I have recently encountered. So today I want list all the possible ways that one can convert an HTML to pdf using python (Django framework).

Let start from basic before going on to Python lets check one of the simplest way to generate pdf using jspdf.

PDF generation using jspdf

For jspdf to work, first of all you will have to link all the required js files to the html.

      
  <script type="text/javascript" src="jspdf/jspdf.js"></script>  
  <script type="text/javascript" src="jspdf/jspdf.plugin.addimage.js"></script> 
  <script type="text/javascript" src="jspdf/jspdf.plugin.cell.js"></script> 
  <script type="text/javascript" src="jspdf/jspdf.plugin.from_html.js"></script> 
  <script type="text/javascript" src="jspdf/jspdf.plugin.ie_below_9_shim.js"></script> 
  <script type="text/javascript" src="jspdf/jspdf.plugin.javascript.js"></script> 
  <script type="text/javascript" src="jspdf/jspdf.plugin.sillysvgrenderer.js"></script> 
  <script type="text/javascript" src="jspdf/jspdf.plugin.split_text_to_size.js"></script> 
  <script type="text/javascript" src="jspdf/jspdf.plugin.standard_fonts_metrics.js"></script> 
  <script type="text/javascript" src="jspdf/jspdf.PLUGINTEMPLATE.js"></script> 
  <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
 

Now give the content (you want to convert to pdf) an id as shown below:

<body>
  <div id="target">
     (your content goes here........) 
  </div>  
  <div>
     <a href="javascript:void(0)" id="cmd">generate PDF</a>
  </div>
</body>
       

Next for the script part:

  
  <script type="text/javascript">
      $(document).ready(function(){

          var specialElementHandlers = {
              '#editor': function (element,renderer) {
                  return true;
              }
          };
          $('#cmd').click(function () {
              var doc = new jsPDF();
              var source = $('#target').html();
              var specialElementHandlers = {
                  '#bypassme': function (element, renderer) {
                      return true;
                  }
              };
              doc.fromHTML(source, 0.5, 0.5, {
                  'width': 75,'elementHandlers': specialElementHandlers
              });
              doc.output("dataurlnewwindow");
          });
      });
  </script>
 

Thats all Folks!!!