Oh wow! I'm impressed that Python 3 is better at each release! On 2 tests, Python 3.7 is faster than Python 2.7, but on test_python_iterator Python 3.7 is still slower. It seems like this specific test became much slower (+19%) on Python 3.4 compared to 2.7.

I guess that your benchmark is on unpatched Python.

I don't think that less_stack.patch has an impact on performances, but I guess because I'm curisous. It seems like it's a little bit faster. At least, it's not slower ;-)

test_python_call: Median +- std dev: [ref] 509 us +- 11 us -> [patch] 453 us +- 49 us: 1.12x faster (-11%)
test_python_getitem: Median +- std dev: [ref] 485 us +- 13 us -> [patch] 470 us +- 23 us: 1.03x faster (-3%)
test_python_iterator: Median +- std dev: [ref] 1.15 ms +- 0.05 ms -> [patch] 1.12 ms +- 0.07 ms: 1.03x faster (-3%)