After a long hiatus I started teaching myself Python, and as a warm-up I wrote a little lambda interpreter in it. I was blown away by how convenient and quick it was in Python, and the project has kind of snowballed to the point where I have most of my previously only vapourware “F♮” functional language up and running (albeit only under a test harness.)

The source is GPL and on GitHub:  https://github.com/billhails/PyScheme