This requires you to full understand upfront all of the code you are trying to convert. While this is feasible in small projects, for a large code base this can

This requires you to full understand upfront all of the code you are trying to convert. While this is feasible in small projects, for a large code base this can be very, very dangerous. The advantages of going the slow way: * you can reuse test-cases * you have something to check the program flow against (in worst case with print statements) * by the time you are done you really should know the code and step #3 is a breeze PS: Your example of "just use jinja2" - have you verified that a rewrite is non-trivial? Have you checked that there are test cases you can run against your code or are you risking to manually have to verify that your new version does the same?