This is really slick. I've used it a few times just to get my capture groups tested right, where pattern matching is needed over parsing. The fact it color codes the Python named capture groups is just awesome: make a regex to match the stuff you need, then slam it into another string via % and you've just converted one string into another. There's tons of ways to do that, but when your patterns are fast and loose, it makes the intent a bit easier to show. (I also tend to use regex with comments, so they tend to be a bit more literate and long... well, at least not all line noise.)
