[int_19h]

Not single byte, but individual fields (float32/int32/string etc). Yes, I expected a much more significant speed-up as well. It's probably because a lot of that code was driven by reflection-type techniques.

Curiously, IronPython did better than anything (but still slow). Haven't tried Jython.

Compiling the whole thing with Cython was less effective than PyPy.

[twa927]

Yes, reflection voids many JIT paths in PyPy, AFAIK. Maybe it was worth rewriting the Python code to get rid of the reflection?