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{"@context":"https://schema.org","@type":"QAPage","mainEntity":{"@type":"Question","name":"Calling long running C# from Python: Do I really need to call PythonEngine.BeginAllowThreads() ?","text":"
The following page https://github.com/pythonnet/pythonnet/wiki/Threading
\nSays:
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However I wrote a simple test and found that calling PythonEngine.BeginAllowThreads() is not required i.e. the Python script is not held up by the call to .NET.
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Python 3.12 code:
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from pathlib import Path\nimport threading\nimport time\nimport pythonnet\npythonnet.set_runtime(\"coreclr\")\nimport clr\n\n\nmy_path = Path(__file__).parent\nassembly_location = my_path / \"SimpleDotNetApiSolution\\\\bin\\\\Debug\\\\net7.0\\\\SimpleDotNetApi\"\nclr.AddReference(str(assembly_location))\nfrom SimpleDotNetApi import SimpleDotNetApiClass\n\n\ndef do_python_work():\n    for i in range(10):\n        print(f\"do_python_work {i}\")\n        time.sleep(0.3)\n\n\nthreading.Thread(target=do_python_work).start()\nsimple_dotnet_api_obj = SimpleDotNetApiClass()\nresult = simple_dotnet_api_obj.DotNetDoWork()\nprint(\".NET returned:\", result)
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.NET 7 code:
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namespace SimpleDotNetApi\n{\n    public class SimpleDotNetApiClass\n    {\n        public bool DotNetDoWork()\n        {\n            for (int i = 0; i < 10; i++)\n            {\n                Console.WriteLine($\"DotNetDoWork {i}\");\n                Thread.Sleep( 1000 );\n            }\n            return true;\n        }\n    }\n}
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Output:
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do_python_work 0\nDotNetDoWork 0\ndo_python_work 1\ndo_python_work 2\ndo_python_work 3\nDotNetDoWork 1\ndo_python_work 4\ndo_python_work 5\ndo_python_work 6\nDotNetDoWork 2\ndo_python_work 7\ndo_python_work 8\ndo_python_work 9\nDotNetDoWork 3\nDotNetDoWork 4\nDotNetDoWork 5\nDotNetDoWork 6\nDotNetDoWork 7\nDotNetDoWork 8\nDotNetDoWork 9\n.NET returned: True\n
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Am I misunderstanding something?
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Code attached: PythonCallingDotNetThreadingTest.zip
","upvoteCount":1,"answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"
In #2209 (reply in thread) @lostmsu answered this question:
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This might be confusing. I believe by default now GIL is not held when .NET code is called from Python. So actually in order to work with any Python objects you have to call and hold Py.GIL().
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The wiki is outdated.
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","upvoteCount":1,"url":"https://github.com/pythonnet/pythonnet/discussions/2424#discussioncomment-11252913"}}}