Work

What next for Carbon Co-op?

A few people have asked me about what is happening next with Carbon Co-op. The short answer is that I have no idea. I had never heard of it before Saturday and I am not very personally invested in it. Probably the best thing to do if you are interested in the future of the business idea is follow the founder on Twitter and ask him.

Now as far as the code that is posted on Launchpad is concerned. I’m going to leave the Sicamp branch exactly as it was when I pushed at 2pm on Sunday. That’s where we go to.

I don’t really like the thought of it but I am tempted to do a screencast to explain the design of the app and show the site and basically all the stuff that wasn’t included in the actually SiCamp presentation. We did a lot of work! We should have shown it!

In terms of the trunk branch I have a few technical questions left of Django that I might use the project to experiment on. These are:

  • Markdown support in descriptions
  • AJAX support
  • Using MySql in the deployed mod_python version (with that done I could open up the app with the understanding it doesn’t do anything).
  • Introducing mocked testing as you would do for a Rails app and off the back of this some refactoring of the views section
  • Replace the Django Template Loader with the Jinja2 equivalent

In terms of the domain problems we set out to solve on the weekend itself, there are two that didn’t get resolved. Firstly there is the Locality issue: who is near who. For the weekend I was going to simply hack it that if the first segment of the post code was the same then those people counted as being in the same area. I’d like to do something more elegant and in depth but that’s another post.

Secondly there is the “ratcheting” idea that was kind of fundamental but I’m not sure really got highlighted in the pitch. The idea is that the app should always be exhorting you to get more people to join and giving you milestones to go for. This means once you have identified all the people in a Locality you need to figure what Actions they are taking and how many people in each Locality are Devoted to the Action.

You then need to see if the Action has Tiers with higher Thresholds and tell the user to try and get their friends and neighbours to commit to the next Tier.

Once you have all the numbers of Ongoing Actions, Devotees and people in the Locality you can then start doing some awesome stuff like altering the postion of the Actions to promote Actions that are close to crossing the next Threshold and so on.

If all that doesn’t make sense then don’t worry because I probably need to explain the design somewhere.

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Python, Web Applications

Django in 24 hours

Last Saturday afternoon I decided to learn Django. It was 2pm on the first day of SiCamp 2008 in London and being the only developer in the room at that point I decided that I should do whatever I felt would be the best option to get an application running by 2pm the next day.

Previously I have done some Google App Engine and the experience convinced me to give Django a go after I found myself, by intuition, creating a GAE project structure of handlers.py (views), models.py and a directory called templates that contained templates. I was then disappointed to find the whole world had got there before me.

So, Django in 24 hours, baptism of fire. What do I think now looking back on the experience?

Everyone has told me that the Django documentation is good and I think I have to concur. Not everything is so clear that when you’re speed reading in one window and typing in another it works first time but importantly nothing in the documentation is actually wrong. When stuff is not working a second, careful look at the documentation got me back on track.

Importantly Django’s core model of web development is sound and intuitive. My editor had around ten files open for the project and the flow of adding something to the application did naturally flow from url to handler to view to model. Maybe the only quibble I have is that the views.py file is deceptively named in MVC terms.

The core of the framework is amazingly concise, I spent the majority of my time thinking about the problem not about the framework API. Binding a URL to function made sense, having to specify a template instead of having one inferred from the method name was maybe my one criticism in the method handler but on the plus side it does allow for flexibility in handling requests. Handing off from one request handler to another was very easy.

Django templates are both amazing and annoying. The syntax and principles are amazing, it was easy to play around with the pages and the template inheritance was really powerful for avoiding duplication. However when I transferred the application from self-serving to mod_python the template generation was very wobbly when compiling changes from the file system. Of course this could also have been mod_python but it was the latest 3 series stable source compiled for the machine. I’ve used Jinja2 previously when generating HTML in Python and might be tempted to stick with it in future.

Django models are great, I hate ORM but I really liked syntax for defining persistence properties and I liked the way that you don’t have the fact that you are really dealing with SQL hidden away from you. It genuinely seemed a more convenient way of expressing the data model rather than an OO wallpaper over relational data storage. I didn’t feel the need to add domain logic to the models but I felt like it wasn’t really polluting the model to do that either.

One thing that didn’t work at all was changing the relations between models; it took me two or three attempts to finally model the relationships between the data concepts. Each time I changed a Foreign Key or Many to Many relationship I ended up deleting the database (SQLite3) as I couldn’t figure how to migrate from the old schema to the new.

One reason for choosing Django was the idea that I wouldn’t have to write the backend code as the admin stuff would be right there for me. It took me a while to get the 1.0 admin to fire up but once it was running it did perform as advertised. One of the attractive things about the application was that the data model followed the conceptual language of the solution in a really powerful way. You could use the admin interface to have a Devotee perform Devotion to an Action. My geek excitement peaked anyway, YMMV.

So them’s the highlights of the experience. Overall Django delivered me a rapid web development process in an intuitive, powerful way and lived up to nearly all of the claims made on the tin. Deploying to Apache/mod_python was painful but most of the pain surrounded the infrastructure of my box (multiple versions of Python, Apache config files) and my lack of mad Apache admin skillz.

I would happily tackle another project in it again.

Perhaps of interest is how the Django development experience matches up against Rails or GAE ¬†which would have been the other obvious choices. GAE would have been very similar but the deployment would have been better and I wouldn’t have had any automatic admin. In retrospect it may have been a better choice for a hack party type event. It certainly would have been my choice for personal projects for easy of deployment but now I have one Django app running perhaps that isn’t as relevant any more. Certainly the thing that has kept me from GAE before, the pain of data migration, doesn’t seem that better in Django (except that you control the datastore and its contents).

Compared to Rails?

  • Admin is much more awesome than scaffolding.
  • Django ORM is much less complex than Active Record, all the data required to create, deploy and use the object is in one place. Django doesn’t have Migrations but has its own brand of database versioning pain.
  • RSpec is awesome (despite its monkey patching of Object) so you aren’t going to beat Rails for easy testing.
  • Django templates are more powerful and easier to use than Erb but you have a lot of Ruby templating options so it’s hard to make a complete comparision. They probably both similar in the sense that you can find a template library that suits your preferences. Django is the purely solution out of the box.
  • Routing and Controllers are much less involved in Django than Rails.
  • Django is less opinionated about how you structure your application directories, which I like.
  • Django doesn’t bake-in AJAX components but is “batteries included”, Rails probably generates better Web2.0 style apps for less effort.
  • Finally Django uses only a few code generators because its basic structure is far less involved. It also generates far less “stuff” for each MVC element which I quite like as I don’t tend to use everything Rails generates.

Okay detailed analysis over, what’s the high-level view? Django and Rails are similar experiences but I think the major differences between them are almost what you could say about Python and Ruby. In Django you are going to get simplicity, clarity and a real choice of how you plug your infrastructure components together. In Rails you are going to get magic up front which is cool but also magic at the back end, which is not cool. Ultimately I think the answer is how opinionated you like your software. Well punk? How opinionated do you like it?

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