Thanks Jeremy. Also wandered off-list w/ Ka-Ping; posting here for posterity. chad ----- chad: BTW, how does the concept of AST transformations relate to the concept of (Lisp) macros? Am I right to think that they are similar? ?!ng: Absolutely. In terms of mechanism, they're basically the same; the main difference is that in Lisp, the transformations are a part of the core language definition. ?!ng: Well, i should refine that a bit to say that the Lisp macro system is a little more specific. Whereas AST transformations in Python are open-ended (you could generate any result you want), the key interesting property of Lisp macros is that they are constrained to be "safe", in the sense that the bindings of variable names are always preserved. chad: Hmmm ... I don't follow python-dev closely but hasn't there been resistance to macros in Python? Are we saying macros may be a good idea after all? ?!ng: resistance -> Yes. ?!ng: good idea -> Not really. AST transformations are useful for experimenting with the language, but i don't think there is much enthusiasm for making these transformations a normal part of the way most programs are written.