Call to Py_Initialize changes signal handler configuration

Environment

Pythonnet version:
2.3.0
Python version:
Python 2.7.13 (v2.7.13:a06454b1afa1, Dec 17 2016, 20:42:59) [MSC v.1500 32 bit (Intel)] on win32
Operating System:
Win 7, 64 bit

Details

What I'm trying to do:
Console application with CTRL+C handling.

According to https://docs.python.org/2/c-api/init.html, Py_Initialize() changes the current signal configuration. In practice, signals like interrupt from CTRL+C in a console application seems to be ignored, which is not the desired behavior. This means that the event handler configured as this Console.CancelKeyPress += Console_CancelKeyPress; does nothing.

It seems Py_InitializeEx(0) should be used for general applications that does not include a python terminal. Alternatively, whether to use the Py_InitalizeEx(0) could be a argument to Python.Initialize()

To reproduce try running this:

class Program
    {
        static void Main(string[] args)
        {
            PythonEngine.Initialize(); // Comment this out to support CTRL+C again.
            Console.WriteLine("Waiting 5s.. Try CTRL+C.");
            System.Threading.Thread.Sleep(5000);
            Console.WriteLine("Done");
        }
    }

@rmadsen-ks

@rmadsen-ks this change looks reasonable! Can you submit a pull request?

@denfromufa, sure, I can do that tomorrow.

Should it be an optional argument to PythonEngine.Initialize?
Should there be a unit test testing the issue? (might be very complicated to implement)

1. Yes According to the linked docs that your provided this Py_InitializeEx should be the preferred way when embedding CPython. However we should keep the old option as optional argument, in case someone handles this somehow with Python exception. So I would add deprecating warning to mention that next version we would switch to recommended C-API behavior. 2. You can actually start your pull request with the unit test to show that the current implementation of Py_Initialize fails to interrupt with Ctrl+C. And then add the implementation once the failure is obviously from both Appveyor and Travis CI. As a side note so you cannot capture Ctrl+C from Python exception currently?

…

On Tue, Apr 4, 2017, 9:48 AM rmadsen-ks ***@***.***> wrote: @denfromufa <https://github.com/denfromufa>, sure, I can do that tomorrow. 1. Should it be an optional argument to PythonEngine.Initialize? 2. Should there be a unit test testing the issue? (might be very complicated to implement) — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#449 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AHgZ5UGc8wGPb78GICB4uAm-FWls9Y3nks5rslg4gaJpZM4MyzCi> .

Fixed pythonnet#449, by added initSigs as an optional parameter to Py…

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Call to Py_Initialize changes signal handler configuration #449

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Call to Py_Initialize changes signal handler configuration #449

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den-run-ai commented on Apr 4, 2017

rmadsen-ks commented on Apr 4, 2017

den-run-ai commented on Apr 4, 2017

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