Victor brought this patch to my attention as the motivation for PEP 509. Unfortunately the patch doesn't apply cleanly and I don't have time to try and piece together all the different parts. From the description on python-dev you linked to there are actually a few different patches that all work together and result in a significant speedup. Is there any chance that you could get all this up to date so it applies cleanly to the CPython 3.6 repo (the hg version!), and report some realistic benchmarks? The speedups reported sound great, but I worry that there's a catch (e.g. memory cost that doesn't become apparent until you have a large program, or minimal speedup on realistic code). This is currently holding up approval of PEP 509.