CPP does many important things for C code that you probably don't need re-implemented. What you seem to be looking for instead may be a templating process that emits C code.
Cheetah is just one of many that allows you to use python. There are others that use python and still more in other languages, but Cheetah is known for being output-agnostic where some templating engines are very heavily geared towards HTML/XML. Do your research.
