If you're talking about the older approach to implementation CPython used to take then I must say if was pretty efficient for what it did (all while keeping the

If you're talking about the older approach to implementation CPython used to take then I must say if was pretty efficient for what it did (all while keeping the code clean). It took a 2-3 days deep dive for a moderately prepared programmer to understand ins/outs of the interpreter. Optimisations coming to Python are a departure from the "clean-first code" approach. It's performance coming at a price of complexity.