As header says: spec_file.h is a mess of different approaches (using external tools, partly using rpm's python bindings, hand-crafted spec-file parsing vs using rpmlib's), inconsistent naming and interfaces.

It should be possible to base all access to the specfile using rpm's python bindings. There's at least one issue, though: current bindings doesn't export the %files list. See [https://bugzilla.redhat.com/show_bug.cgi?id=857653]