Maybe sibling is referring to an aspect of Python I'm not aware of (there are probably many), but much of the book (or at least the first edition) is language-agnostic. Tasks are pretty well partitioned into front-end, optimization, and back-end sections (further, really), with the idea that each segment of the compiler doesn't have to worry much about other segments' tasks (e.g. code shape is not the concern of the parser).