logopy

logopy is an interpreter for the Logo programming language written in Python3. Logo is often associated with Turtle Graphics, and logopy integrates with Python’s own turtle module.

I developed logopy after my son (then age 11) got a book from our local library about computer game programming. The first few chapters were all about Logo, while the later half of the book focused on Python.

Unfortunately, the book recommended Windows based interpreters, and we don’t run Windows OS at home. Poking around on my Linux workstation, I found UCBLogo in the software repositories, so I installed it and fired it up. My son had fun making shapes while I went on to do something else.

Later on, after seeing some of the programs he had typed in from the book, I had a bit of nostalgia for when I was in grade school and I had entered commands to direct the turtle on the Apple IIe’s in my school’s computer room. I started writing some of my own commands to wow my son.

UCBLogo performed pretty well, but a couple of times the program crashed, and there were some features I wished it had. Eventually, I thought, “Someone must have written a Logo interpreter in Python! I mean, it already has the turtle graphics built in!”. A bit of searching found Ian Bicking’s pylogo. I was intially excited, but I had a bit of trouble getting it up and running. Trying to run it under Python3 failed, and the code looked like it hadn’t been updated in quite some time.

That is when I had the ridiculous notion that writing my own interpreter would probably be much easier than trying to update the existing code. I told myself, “Oh, I’ll try to throw something together in an hour. If it goes longer than that, I’ll just forget this Logo business …” I kept telling myself that during countless snatches of free time I found myself working on this project.

Ultimately, I think the reason I kept working on it is because of something Seymour Papert, one of the inventers of Logo had written. He argues that people learn things by doing, and by making connections [1] . For me, programming is a process where I make all sorts of connections about what is going on in a system. The errors and mistakes actually make me slow down and think about what is going on. Why did the tokens parse this way? Why did the intepreter choose to evaluate this way and not that way? Let’s see if I can get this to draw a square. Good, now a triangle? Easy! An ellipse? Hmm, that is a bit harder. I’m going to have to really think about this one. Am I going to have to pull out an old geomtry textbook? And so on.

Eventually, I’ve gotten the project to a state where is not so frustrating to use, and it can actually be fun to see my logo programs move the turtle around. I hope that anyone else who also enjoys Logo programming thinks so, too.

Footnotes

[1]	In The Children’s Machine Rethinking School in the Age of the Computer, Papert devotes an entire chapter to suggest that the deliberate part of learning is mostly about making connections between mental artifacts that already exist in our minds.