cc @hroncok

I tested manually https://github.com/konlpy/konlpy test suite with this JPype fix: Python doesn't crash anymore! My PR fixed my bug.

I also reported the issue upstream: https://bugs.python.org/issue33932

cc @marscher

Note: I'm a CPython core developer.

I trust you and my CI, was just waiting for it to pass. Thank you very much for your patch!

I guess we need to cut this jpype release soon...

Does the PyEval_InitThreads() belong in the module initialization as well? The CPython documentation wasn't clear if this was a module thing or just part of the python startup.

Does the PyEval_InitThreads() belong in the module initialization as well?

You have to keep this call.

We enhanced the documentation in Python 3.7:
https://docs.python.org/dev/c-api/init.html
"Note: The following functions should not be called before Py_Initialize(): (...) PyEval_InitThreads()."

Moreover, we did another change in Python 3.7:
" void PyEval_InitThreads(): (...) Changed in version 3.7: This function is now called by Py_Initialize(), so you don’t have to call it yourself anymore."

On Python 3.6 and older, it's a good thing to call this function to prevent race conditions when spawning threads in C which then uses the Python API.

Changed in version 3.7: This function is now called by Py_Initialize(), so you don’t have to call it yourself anymore.

Oh, and if you are curious, I wrote an article about this specific change :-) https://vstinner.github.io/python37-gil-change.html

That's very cool! Congrats for nailing this nasty one down 😎

@marscher We likely need to hit the known defect on the arrays considering everything with the same size as being directly convertible before cutting a release. But it will be a week or two before I can get back to that.

While removing the Py_Initialize() is safe and fix a bug in Python 3.7rc1, FYI I fixed the future Python 3.7.0 final to allow again to call Py_Initialize() twice. But Nick Coghlan still plans to deprecate this behaviour, in the future calling Py_Initialize() twice will fail (as Python 3.7rc1).