How do I get the current PyInterpreterState?

Question

I'd like to create a PyThreadState since there doesn't appear to be one for the current thread.

How do I get the current PyInterpreterState to pass to PyThreadState_New(...), or is that something that I should only do if I'm embedding an interpreter (and thus have created it), rather than calling into a library from python?

score 4 · Answer 1 · answered Jul 07 '11 at 12:43

I guess that you might are doing multi-threads programming. Recently, I'm having the similar problems. Hope the following codes may help you.

//in main thread
PyThreadState * mainThreadState = NULL;

Py_Initialize();
PyEval_InitThreads();
mainThreadState = PyThreadState_Get();
PyEval_ReleaseLock();

//in threaded thread
PyEval_AcquireLock();
PyInterpreterState * mainInterpreterState = mainThreadState->interp;
PyThreadState * myThreadState = PyThreadState_New(mainInterpreterState);
PyEval_ReleaseLock();
/*
 * embeded python part 
 * PyEval_CallObject() for example
 */

ncoghlan · Answer 2 · 2011-02-15T05:11:12.327

1

If you are attempting to call back into Python from a non-Python created thread, then you can use the PyGILState_Ensure() API. This takes care of creating a temporary thread state if the current thread doesn't already have one.

See http://docs.python.org/c-api/init.html#non-python-created-threads for more details.

Releasing the GIL in code that is called from a Python thread is even easier using the Py_BEGIN(/END)_ALLOW_THREADS macros: http://docs.python.org/c-api/init.html#releasing-the-gil-from-extension-code

edited Feb 15 '11 at 05:11

answered Feb 14 '11 at 01:43

ncoghlan

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The problem is actually the reverse: calling from python into a library, during which time I want to allow other python threads to run. – James Feb 14 '11 at 08:29
In that case, you probably want the Py_BEGIN_ALLOW_THREADS and Py_END_ALLOW_THREADS macros: http://docs.python.org/c-api/init.html#releasing-the-gil-from-extension-code – ncoghlan Feb 15 '11 at 05:09
These macros expand to calls to PyEval_SaveThread and PyEval_RestoreThread, which need a PyThreadState to exist for the current thread. It turns out that the fact I don't have a PyThreadState is, in fact, a fatal error. – James Feb 15 '11 at 09:46

score 1 · Accepted Answer · answered Feb 15 '11 at 09:48

1

It turns out that not having a PyThreadState in the main thread is a fatal error. It was caused for me by two different python versions both being linked at the same time, so this question is somewhat moot.

answered Feb 15 '11 at 09:48

James

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How do I get the current PyInterpreterState?

3 Answers3