Interesting extension of this exercise would be to replace your custom AST with the AST exposed by Python, then use the compile() builtin to compile said AST into a PyCodeObject ready for direct execution by the Python VM. :)

Something along these lines: https://github.com/thomaslee/viking-poc/blob/master/viking#L...

(Disclaimer: I wrote the Python-AST-to-PyObject transformation code for Python 2.6 that made this sort of stuff possible -- fun hack!)