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

[Tony Roberts]

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> 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"))
>
>     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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