I'm a knitter as well as a math and computer science enthusiast. Although I don't regularly write code in the perl programming language (actually, I find it terrifying), I do frequently use the purl stitch in my knitting. And the title "Knit and Python" just doesn't have the same ring to it.
Sorry to everyone who spelled purl (the stitch) wrong and came to this site trying to figure out how to do it. You'll have to look here for that pearl of wisdom.