long time ago i had similar need.. did not want to directly churn SQL, for hundreds of small filters. So i did an expression parser and translator, and wrote all things in simple python functions, then translated those into SQL automatically. Both funcs and the translator were heavily tested. Apparently, that parser also grew few other "renderers" - like evaluator, documenter and what not.

https://github.com/svilendobrev/svd_util/blob/master/expr.py