PyObject to NDArray

[aaronavi]

Hi
I have a PyObject which is of a PyDict type, It contains an NDArray, i need to convert it to actual NDArray.

How can i do that?

Thanks

[Nucs]

@aaronavi, sorry for the very late reply. With the new NumSharp.Interop.pythonnet package (0.70.0, #628) you can pull the array straight out of the dict.

Set up the Python engine once at startup - either point pythonnet at an installed Python, or deploy one from NuGet with Python.Included (no system install needed):

using NumSharp;
using NumSharp.Interop.PythonNet;
using Python.Runtime;

// Option A - existing Python: the PYTHONNET_PYDLL env var, or the DLL directly
Runtime.PythonDLL = "python312.dll";   // or Environment.GetEnvironmentVariable("PYTHONNET_PYDLL")
PythonEngine.Initialize();

// Option B - deploy an embedded Python from NuGet (dotnet add package Python.Included)
await Python.Included.Installer.SetupPython();
await Python.Included.Installer.PipInstallModule("numpy");
PythonEngine.Initialize();

Explicit:

using (Py.GIL())
{
    // pyDict is your PyObject (a Python dict) holding a numpy array
    PyObject arr = pyDict["weights"];   // the ndarray, still a PyObject
    NDArray nd = arr.AsNDArray();        // -> NumSharp NDArray
    Console.WriteLine(nd.shape[0]);      // 4
}

Implicit (register the codec once, then use pythonnet's own As<NDArray>()):

NDArrayPythonInterop.RegisterCodec();   // once per process

using (Py.GIL())
{
    PyObject arr = pyDict["weights"];
    NDArray nd = arr.As<NDArray>();      // implicit decode via the codec
    Console.WriteLine(nd.shape[0]);      // 4
}

Requires NumSharp.Interop.pythonnet (dotnet add package NumSharp.Interop.pythonnet). Closing.