The time has come for me to finally use a python web framework, Pylons is the choice around here. I’ve set up a few toy apps using it but nothing so involved that took real software planning. Since I was making a real application that required real business planning I found the Pylons documentation to be really screwed up. The instructions in the tutorials conflicted with each other in how to set up the websetup.py, development.py, etc. Months ago I had a toy program setup in half an hour using one tutorial; today it took me over two hours because the Pylons docs had changed. But not across the boards.

While displeased with this, I’m used to it. It also means that serious research is needed in order to work with the software. Being fully involved with Pylons, albeit new. I didn’t expect it to be RESTful; nor did I expect it to allow different extension type within an action. I am actually impressed with the Ruby on Rails RESTful implementation and was very surprised to find that Pylons itself has RESTful implementations itself.

However, my project requires me to call one action in the extension with “.js” for JSON and another extension of “.rss” for that version. The Pylons RESTful documentation lacks for this. I couldn’t find any other reference for this on the web either. While I don’t know for sure when Pylons added RESTful resources the documentation lacks any examples that I found for using different formats, so here it goes.

The Pylons wiki for RESTful controllers is found here: How map.resource enables controllers as services. It explains everything you want to know about how to use REST within Pylons. It does not explain my predicament on how to make the index action display JSON format or RSS format.

After a little testing and discovery I found out that you can, within an action, produce different views specific to the format of the action.  Given my requirements here is how I was able to use one RESTful action for many formats, i.e (.js, .gif, .rss, .rtf, etc).

1. Create your RESTful controller using the command: paster restcontroller <singular name> <plural name>
This is no different than the instructions in the map.resource link above.

2. In the action create an if…elsif…else to actually control the format:
def index(self, format=”html”):
if format == “js”:
response.headers['Content-Type'] = ‘application/javascript’
return render(’/pubscript/indexjs.mako’)
elif format == “xml”:

response.headers['Content-Type'] = ‘application/xml’
return render(’/pubscript/indexxml.mako’)
else:
abort(404, ‘Page Not Found’)

So as the index definition provides that any index call to the controller does perform the action, only the .js returns an js (JSON) file or an .xml renders an xml file format. Any other format or none provided sends a 404 File Not Found error. Now I had complete control of what the format is and control of any unexpected calls.

Pylons has evoled to the presedence set by Ruby on Rails in that RESTful controllers can be used. Even though the default format for Pylons is HTML you can detect such as present different formats based upon such.  Being new to the Pylon framework itself I wasn’t expecting this functionality. Discovering that it has it, and is acting on the different formats, I do believe that it has emerged as a mature framework that embraces best practices of web application programming.

Still highly complicated in setting up and a huge learning curve with little correct documentation though, don’t get me wrong there.

Tags: framework, model-view-controller, mvc, pyhton, pylons, restful