But all four of us are paying for stuff for all four of us, it does make keeping track of money a little tricky. The traditional solution is for everybody to stuff their receipts into a drawer, and every month you all sit down and slowly work your way through the receipts.

Each of us owes you $50 for your grocery run, and you owe me $20 for my grocery run.

It’s a painful process, and the difficulty scales super-linearly as you add more people. Even with four, it would be pretty bad.

Now, it turns out that programmers hate tedious tasks like that, so there’s a long history amongst my friends of programmatically solving this in various ways. When we moved into this apartment, I figured I’d try my hand at it, and BlueChips is the result.

Since we set it up, BlueChips has been used by us and by other roommate setups to manage their expenses. We use it for tracking everything – rent, utilities, groceries, furniture, when all of us go out for dinner…

BlueChips has a very simple data model. There are users. A user can move money in two ways: expenditures and transfers. In an expenditure, one person spends money on behalf of a bunch of people. As a result of the expenditure, each of those people owes the spender some amount of money. BlueChips lets different people owe different amounts as the result of a single expenditure. For example, when we pay rent, each of us pays a different percentage, and BlueChips can follow that.

BlueChips’ biggest feature, though, is its ability to calculate the transfers necessary to settle the books. When it makes this calculation it also does something we call “pushing transfers”. Let’s say Larry owes Moe $1, and Moe owes Curly $1. BlueChips can “push” the $1 through, and will tell you that, to settle the books, Larry should give Curly $1.

If you’re still confused, or just want to see what the app looks like, I have a demo instance running at http://demo.bluechi.ps.

The software’s been around for a year, and it’s been open-source for most of that time, but I’ve never quite gotten around to putting a finishing coat of polish on it and getting it into a form that other people can use it.

When I lived with Scott Torborg and some other friends over the summer, we used BlueChips again for handling finances. Scott decided to put some of that polishing effort into BlueChips, and I have him to thank for all of the styling, excellent test coverage, and the iPhone interface, along with innumerable other tweaks.

I finally coded up the last big feature that BlueChips was missing: the ability to add new users without directly interacting with the database.

And so today I’m pleased to announce that I’ve tagged and released a version 1.0.0 of BlueChips.

BUT WAIT! THERE’S MORE!

For those of you MIT folks, I’ve worked with the scripts.mit.edu team to provide a Scripts autoinstaller. To install BlueChips, you can run the following commands from any Athena workstation:

dr-wily:~ broder$ add blue-sun
dr-wily:~ broder$ scripts-bluechips

Please remember that this is not a Scripts-managed autoinstaller. If you run into any problems, like it says, please let me know at bluechips@mit.edu.

And if you find BlueChips to be missing a feature you want, please feel free to write it yourself! In general, I don’t expect to have a lot of time going forward for new feature development, but I’m more than willing to review contributions from others. It’s my hope that the community can pick up my slack and keep BlueChips moving forward.

Apparently Python is trendy these days! I was in a room that seats 65 or so people, and there were lots of people sitting in the aisles.

In spite of being somewhat intimidated by the large audience, and struggling to hit my stride during the beginning of the talk, I think I did a much better job this year once I actually started covering linguistic constructs. In spite of not spending a lot of time preparing this year, I had good notes for the first lecture from last year. But more importantly, I felt like I knew Python better, which really made the difference. I thought that my discussion was more focused, more concise, and more clear.

The room was an impressive mix of skill levels – several people who had never programmed and a few people who had clearly been doing it for years. Both groups asked very good questions as well.

Hopefully I’ll get to spend more time preparing for the next class, because my notes from last year get worse as I get further into the class.