Living Code

I really need to start blogging these before they happen, but I will at least try to summarize the January Vancouver Python user group meeting. Our featured speaker wasn’t able to make it, and it was only with the nudging of Andy and the gracious help of Jim and Dane at Workspace that we even had a January meeting. But a meeting was had, a surprising number of people braved the heavy rain, and we had a good time talking about our varied interests and explorations, mostly with a Python theme.

What I did over winter vacation

We had an open discussion, starting with the nominal topic of the night, Python packaging. We discussed some of the pros and cons of distutils, setuptools, and easy_install. Our casual conclusion was that all of these tools work better if you first use Ian Bicking’s VirtualEnv to prevent library pollution in your main Python install. VirtualEnv puts a copy of Python, your required libraries, and any dependencies they have into a separate directory and then runs from that, keeping a project nicely sandboxed. The OS X Python application builder py2app, works similarly, but after the fact as a final build step so you can deliver a complete application without worrying what version of Python and libraries are installed on a user’s computer. Ian Bicking also has package installer you can use with (or without) VirtualEnv, called Pip, and if you check his two links here you may notice a pattern forming for his blog titles.

From there we wandered around, topic-wise, discussing XML/HTML parsing libraries such as Beautiful Soup and lxml, from there to screen scrapers like mechanize, to web spiders like scrapy.

Conversation drifted into 3D for a bit, touching on VRML/X3D and the open-source FreeWRL viewer (built by the Canadian Government, yay!). While it isn’t really a Python project, there is a Python library to generate VRML as part of the Scientific library (not to be confused with SciPy. And if you don’t want to go the XML route, you can stay in Python because Scientific can also generate VPython code (although VPython does not yet support things like transparency or texture mapping).

We kept coming back to web frameworks, discussing the tradeoffs between Django and Zope/Plone and the impact of “cloud computing” platforms such as Amazon Web Services (AWS) and Google App Engine. While the AWS services give a lot more flexibility, they require a substantial amount of planning and configuration. App Engine has the easy deployment of a PHP app, but with the convenience of Python and the power of Big Table, but the rather substantial disadvantage of still being a beta environment that you can’t actually buy services on yet (no scaling up).

There are some workarounds for these and other problems (the App Engine 10 app limit, for instance). Hadoop was mentioned as an open-source alternative to App Engine. Amazon Machine Images can give you a head start at deploying on AWS, although you will still need to make arrangements for data persistence. 10gen appears to be building using the App Engine model (more or less), but as a smaller player, they may be more responsive to user feedback. LowEndBox is not a provider, but a blog tracking ultra-cheap hosting with root access, so you could conceivably build your own AWS on a shoestring.

Since I spent part of the holidays building Lego Mindstorms models with my kids (a machine gun and a puppy), I kept trying to steer the conversation towards robotics. Unfortunately, the Python Robotics project does not support Mindstorms yet, but they do support Roombas, so I may still be in luck. I haven’t found a Python project for programming Mindstorms yet, but you could probably wrap Not Exactly C with Python fairly easily, and after the meeting I found this script to use Bluetooth to control Mindstorms from Python.

After that we continued the discussion at the pub and I don’t have any browser history to help me remember that part of the discussion. I do remember that before the meeting started, I did plug Scratch again as the best way to introduce 6-12 year olds to programming.

Finally, I want to thank everyone on the VanPyZ mailing list for helping to organize and to re-establish the group’s web site after recent hack attacks and crashing, especially Henry Prêcheur for restoring the content and moving it to the official Python wiki for the new VanPyZ page.