On Wed, 18 Dec 2013 00:19:23 +0100 Daniel Pocock <daniel@pocock.com.au> wrote:
If a main thread does things like importing a module and obtaining a reference to a Python method, can those things be used by other C++ threads or do they have to repeat those lookups?
The C++ threads must use the PyGILState API to initialize corresponding Python thread states, and to hold the GIL. However, you don't have to *repeat* the lookups - pointers valid in one thread are valid in other threads, as long as you own a strong reference to the PyObject (beware functions which return a borrowed reference).
Is there any logic that needs to be executed once only as each thread is started? (the doc suggests just PyGILState_Ensure/PyGILState_Release each time a thread accesses Python methods - is there anything else?)
If you use the PyGILState API, there shouldn't be anything else.
(e.g. should users always explicitly call PyEval_InitThreads() in their main thread or worker threads or both?)
You only need to call PyEval_InitThreads() once in the main Python thread. Regards Antoine.