I’m currently experimenting with a pyramid site at work. Why not Django, which we use for everything else?
(For Pyramid, see a summary of a Dutch Python usergroup meeting talk about Pyramid.)
Well, our current system (called Lizard) is a big structured collection of Django apps.
This gives you a generic layout with a header, sidebar, the correct colors. Lots of stuff to make it easy to quickly build your project (once you buy into the basic structure and learn to work with it).
“Lizard-map” builds upon lizard-ui and adds map views. Geographical information. Some “adapter mechanism” that basically provides an interface to connect any kind of data source to our map mechanism.
There are quite a lot of data sources that we’ve mapped to maps this way. Rendering it, querying, returning a location’s CSV data, a location’s flot/matplotlib graph, combining various data sources, etc.
Great to get going, but you do have to get to know the underdocumented interface. And it is clunky in places.
“lizard-something”. Lots of apps (40 or so) that use lizard-ui for the UI and lizard-map for the map stuff.
The good thing: we’ve created 20 or 30 sites based on this structure. Mixing various Django Lizard apps. Works like a charm.
Why this structure? We made it collaboratively, but there’s a big piece of me at the core. I’m used to base templates (through Plone). I’m used to lots of python packages (so I introduced buildout/setuptools/pypi). I’m used to having a structure to work in. Etc.
Why? Well, if you know “belbin team roles” you can look at mine. One of my regular roles is “shaper”. Melodramatically you could translate that with “Reinout, bringer of structure”...
The good things basically comes from using Django as far as possible:
static/lizard_ui/logo.pngin your site to override lizard-ui’s default one.
The bad and suboptimal also come from using Django as far as possible:
It all works because it is such a high stack. That’s also the problem. You need to buy into the whole stack and you need to work with the whole stack. And you need to get to know the whole stack.
The code and the templates belong together. Templates have an inheritance tree; the view code also. A template needs the view that belongs to it. A view prepares what the template needs.
Everything you do pulls in the whole universe. To get your app’s view and template to work, your app depends on lizard-ui and lizard-map. Which pulls in matplotlib (for the graphs), mapnik (for custom map rendering), etc. And a whole bunch of geo libraries. Even if you don’t need them in your app.
Lizard does almost everything with inheritance. Inheritance of view code and inheritance (if you can call it that way) of templates. Django makes that easy with class based views and with blocks in templates. At least, it looks that way to me.
From reading Pyramid documentation I get the impression that composition is a way better structuring mechanism than inheritance. I have to think about this: would it improve Lizard’s structure? It sounds very plausible.
So... the drawbacks of a tightly integrated view + template + static files collection of Django apps are now bigger than the gains (speed of development/integration) we get from it. At least, those drawbacks are internally strongly suspected to restrict us, that’s why we’re experimenting.
A quote from Jacob Kaplan-Moss’ keynote at last year’s djangocon.eu conference serves well as an illustration:
Lots of buzzwords. Real-time. Ask beyond the hype and ask what lies behind them. People in this case want responsive apps. More desktop-like responsiveness. More interaction.
The critisism: this all is hard to do in Django. The state of the art is, sadly, parallel MVC stacks. Django on one side, Backbone on the other. Syncing them. “It is hard” as in “there are fundamental parts design decisions in Django that work against it”.
Brainstorming, there is already something in Django. You can already push the context a bit further down the line intead of baking it directly into a template. Cannot we push it even further? Into the browser with some automatic bindings? Just brainstorming.
This illustrates the problem. Are we dinosaurs when using a Django template?
So in the project I’m currently working on we’re now doing it all new. Static html/css/js project made by our UI expert. And he’s going to define what he needs out of the REST API.
Conclusion is that we no longer need templating and staticfiles on the server side. What’s left, then, of Django? ORM/models and views.
If we’re experimenting anyway, why not write the Python part in something else than Django? Due to my background Pyramid was an easy choice. Very small Python web framework with a solid structure and a good extensionability story.
It’s experiment time! (But in the end there’ll have to be a new structure again for all of our projects. Our business is not sustainable if we have to build everything from scratch the whole time. But perhaps that composition-instead-of-inheritance idea helps us there to set it up in a better way.)
My name is Reinout van Rees and I work a lot with Python (programming language) and Django (website framework). I live in The Netherlands and I'm happily married to Annie van Rees-Kooiman.
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