[Python.NET] Python.Net for Python3: bug when using an embedded interpreter

[Serge WEINSTOCK]

Thanks, it’s working fine.

I’ve created a pull request for handling Python3 int conversion to int32 in 32 bits python interpreters. Could you have a look at it?

Serge

From: pythondotnet-bounces+serge.weinstock=uk.bnpparibas.com at python.org [mailto:pythondotnet-bounces+serge.weinstock=uk.bnpparibas.com at python.org]
Sent: 30 September 2014 19:16
To: pythondotnet at python.org
Subject: Re: [Python.NET] Python.Net for Python3: bug when using an embedded interpreter

Should be fixed now. Please re-open if it's still a problem (https://github.com/renshawbay/pythonnet/issues/13).

cheers,
Tony

On Tue, Sep 30, 2014 at 4:57 PM, Tony Roberts <tony at pyxll.com<mailto:tony at pyxll.com>> wrote:
Hi Serge,

I see what you're saying. It would think that bit just needs to be moved until after we're sure python has been initialized so it works in both cases. I don't see any need to move it into a separate python module; having it compiled into one is cleaner IMHO. If you're not subclassing .NET classes in python and so don't need python methods/properties reflected to .net you won't need it anyway, so you could just remove that bit of code from your fork for now.

I'll take a look, but if you get round to it before I do then please feel free to submit a pull request. I'll create an issue in github so it doesn't get forgotten.

thanks,
Tony


On Tue, Sep 30, 2014 at 11:59 AM, Serge WEINSTOCK <serge.weinstock at uk.bnpparibas.com<mailto:serge.weinstock at uk.bnpparibas.com>> wrote:
Hi Tony,

You recently made a change which prevents me using the library in an embedded Python interpreter.

In pythonengine.cs, you “inject” decorators with the following code:

//=================================================================
public static void Initialize() {
.....
IntPtr globals = Runtime.PyEval_GetGlobals();
PyDict locals = new PyDict();
try
{
    IntPtr builtins = Runtime.PyEval_GetBuiltins();
    Runtime.PyDict_SetItemString(locals.Handle, "__builtins__", builtins);

    var assembly = Assembly.GetExecutingAssembly();
    using (Stream stream = assembly.GetManifestResourceStream("Python.Runtime.resources.clr.py<http://Python.Runtime.resources.clr.py>"))
    using (StreamReader reader = new StreamReader(stream))
    {
        // add the contents of clr.py to the module
        string clr_py = reader.ReadToEnd();
        PyObject result = RunString(clr_py, globals, locals.Handle);
        if (null == result)
            throw new PythonException();
        result.Dispose();
    }
//=================================================================
When running from a Python script, it’s fine because the Python interpreter has already been initialized and global variables have been defined.

The issue is that when running from an embedded interpreter. As I must first initialize the Python engine using PythonEngine.Initialize().

So when we reach this piece of code, there is no script running, no “Python context”, so “PyEval_GetGlobals” returns null and “RunString” fails.

We could create an artificial global dictionary but it won’t be available to the rest of the code.

I think it should be best to move this code into a Python module. If run from a script (PyEval_GetGlobals() != null), you could inject the decorators with a simple “from decorators_pythonnet import *”. If run from an embedded interpreter, we could add a line for running the same code once the engine has been initialized.

What do you think?

Serge Weinstock


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