You are using Apache to serve content, right? If that's the case, the Mod_python module (an Apache module, not a Python module) provides PSP (Python Server Pages) functionality - just what you'd need to replace your JSPs. You can get more information on this platform by following these links:
As for a line-by-line Java-to-Python converter? I think you might be out of luck on that one. Your best bet is to learn PSP and the basics of inline programming (if you don't know them already) and then get help for the JSP stuff. I used to do a fair amount of JSP programming, so if you have specific questions you can try me or you can ask the people in the Java or JSP forums, who are bound to be much more knowledgeable.