Allowing Ctrl-C to interrupt a python C-extension

Question

I\'m running some computationally heavy simulation in (home-made) C-based python extensions. Occasionally I get stuff wrong and would like to terminate a simulation. However

Answer 1

Python has a signal handler installed on SIGINT which simply sets a flag that is checked by the main interpreter loop. For this handler to work properly, the Python interpreter has to be running Python code.

You have a couple of options available to you:

1. Use Py_BEGIN_ALLOW_THREADS/Py_END_ALLOW_THREADS to release the GIL around your C extension code. You cannot use any Python functions when not holding the GIL, but Python code (and other C code) may run concurrently with your C thread (true multithreading). A separate Python thread can execute alongside the C extension and catch Ctrl+C signals.
2. Set up your own SIGINT handler and call the original (Python) signal handler. Your SIGINT handler can then do whatever it needs to do to cancel the C extension code and return control to the Python interpreter.