Mailman 3 September 2019 - Python.NET

Python for .NET working group meeting notes from Tuesday, September 24, 2019
by Mark Visser 18 Oct '19

18 Oct '19

Attendees: Mark Visser (Unity), Benoit Hudson & Felix Bourbonnais (ImgSpc), Victor Milovanov, Mohamed Koubaa (ANSYS Inc), Amos Li Agenda 1. (Mark) Suggest we use a "needs discussion" label on issues and PRs for next time. Then we can just go through them on the call. 2. (Mark) Can we get a status update on joining the .NET Foundation? Github issue: Joining the .NET Foundation <https://github.com/pythonnet/pythonnet/issues/956> 3. (Benoit) Python can't reliably re-initialize; new proposal for Unity's domain reload <https://github.com/pythonnet/pythonnet/issues/957> 4. (Benoit) What's the policy with the GIL? Main thread appears to be grabbing the lock and not releasing it. 5. (Mohamed) Can I get clarification on IWrapper vs. reflection for PR #808? Notes Welcome to new contributor Mohamed Koubaa (ANSYS), who is investigating moving his company's platform from IronPython to CPython. 1 & 2) need input from Benedikt, Mark will follow up with Benedikt. 4) Benoit: GIL - Should we expect the GIL to be held after initialization? Victor: I wouldn't expect it to be held. [PyGIL] attribute is informational. 3) Benoit: Python can't reliably re-initialize. last fall's work - force PyFinalize to be called unfortunately doesn't work for native extensions - can't reliably reinitialize proposal instead of calling PyFinalize, delete all links from Python to C# Felix prototyped a solution that tracks all links during proxy generation and cuts all links during domain shutdown to prevent dereference of dead pointers result is just AttributeError instead of crash Amos proposed a different solution which seems to be targeting memory leaks Victor: what about memory leaks? C# side deletes all of its memory If C# holds a reference to Python, it will still exist when C# shuts down - no problem Amos: has a branch that solves one of the problems Benoit & Felix will investigate his branch and see where it intersects with their solution the reason we're using pythonnet is to enable PySide/PyQt and numpy among others 5) Mohamed: Working on a small change to implement the wrapper function for console output via __repr__ https://github.com/pythonnet/pythonnet/pull/808 inheritance over reflection, IWrapper vs. method with a signature Pythonnet can reflect what are the pros and cons? should we go with a convention? Victor: you can take the reflection approach, but need to cache the delegates more of an implementation detail, not actually necessary (note: any errors in the above are mine, feel free to correct any gross misrepresentations I've inadvertently made!) Action Items Mark follow up with Benedikt about Python foundation and using issues to track discussion items Benoit & Felix investigate why GIL is held indefinitely test out Amos's branch and connect over gitter to discuss what parts of the problem each approach is solving Thank you all for attending! The next call will be held at 3pm EST on Tuesday, October 8th, 2019, see you then. Please e-mail me if you're not on the attendee list and I will add you. Mark Visser Tooling Dev Manager Unity Technologies - www.unity3d.com <http://www.unity3d.com/>

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Call for discussion items for next week's working group meeting (September 24th)
by Mark Visser 24 Sep '19

24 Sep '19

Hi all, The next Python for .NET working group call will be held on Tuesday, September 24th, at 3pm EST / 12pm PST. Please reply to this e-mail with any discussion items you would like to add to the agenda, or if you would like to be added to the call. Mine: 1. I suggest we use a "needs discussion" label on issues and PRs for next time. Then we can just go through them on the call. 2. Benedikt (filmor(a)gmail.com <mailto:filmor@gmail.com>) can we get a status update on joining the .NET Foundation? Github issue: Joining the .NET Foundation <https://github.com/pythonnet/pythonnet/issues/956> cheers, -Mark Mark Visser Tooling Dev Manager Unity Technologies - www.unity3d.com <http://www.unity3d.com/>

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Working group meeting Tuesday September 10th
by Mark Visser 12 Sep '19

12 Sep '19

Hi everyone, Here are the minutes from Tuesday's meeting. Present: Victor Milovanov, Amos Li, Mark Visser Mark mentioned that his team has found a solution to C# domain reload that doesn't crash the Unity Editor. Benoit Hudson will join the next meeting to discuss with the group. Victor has been working on the ability to inherit C# classes from Python classes and override Python methods in C# using attributes. The next meeting will held on Tuesday, September 24th at 3pm EST. If you have not received an invite, please e-mail me directly and I'll add you to the event. Also please note that I went ahead and switched to Zoom for hosting meetings as Google Hangouts is blocked in the PRC. I'll ask the list for agenda items the week before the meeting. Hope to see you all online next time. cheers, -Mark Mark Visser DCC Team Lead Unity Technologies - www.unity3d.com <http://www.unity3d.com/>

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Memory management when embedding python.
by Thomas Lundgaard Hansen 11 Sep '19

11 Sep '19

Hi. I am embedding Python into a .NET (C#) application. For the purpose of this discussion my code is like the example given here: https://github.com/pythonnet/pythonnet#example (except that I am working with arrays of a substantial size). Each of the "dynamic" variables created in that example are of the .NET type PyObject, which is a disposable type. The code in the example does not call Dispose() on these objects and it would indeed be very inconvenient to do so. Whats the best practice here and what considerations went into this design? Can we expect that the only unmanged resources held by PyObject's are unmanaged memory? (Unless, of course, the PyObject represents a system resource like a file or network stream). Has it been considered to use GC.AddMemoryPressure when PyObjects are backed by a large amount of unmanaged memory? Thanks, Thomas Lundgaard Hansen

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