how to make NumSharp.NDArray from Numpy.NDarray? #416

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1. djagatiya

   closed this as completedon Jul 6, 2020
2. djagatiya

   changed the title [-]is there any way to convert NumSharp.NDArray to Numpy.NDarray?[/-] [+]how to make NumSharp.NDarray from Numpy.NDarray?[/+] on Jul 6, 2020
3. djagatiya

   reopened this on Jul 6, 2020
4. djagatiya

   changed the title [-]how to make NumSharp.NDarray from Numpy.NDarray?[/-] [+]how to make NumSharp.NDArray from Numpy.NDarray?[/+] on Jul 6, 2020
5. djagatiya commented on Jul 7, 2020

   

   djagatiya

   on Jul 7, 2020

   Author

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   I found a solution, but is this the right way to do it?

   Numpy.NDarray numpyArray = Numpy.np.random.randn(224,224,3);
   byte[] v = numpyArray.GetData<byte>();
   fixed (byte* packet = v)
   {
       var block = new UnmanagedMemoryBlock<byte>(packet, v.Length);
       var storage = new UnmanagedStorage(new ArraySlice<byte>(block), numpyArray.shape.Dimensions);
       NumSharp.NDArray numSharpArray = new NumSharp.NDArray(storage);
   }
   
6. Nucs commented on Sep 7, 2026

   

   Nucs

   on Sep 7, 2026

   Last edited by Nucs

   Member

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   @djagatiya, your manual UnmanagedMemoryBlock approach worked, but the new NumSharp.Interop.pythonnet package (0.70.0, #628) makes it a one-liner, zero-copy (strided/offset included, read-only stays read-only).

   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())
   {
       dynamic np_ = Py.Import("numpy");
       PyObject npArr = np_.arange(4);   // a numpy array
   
       NDArray nd = npArr.AsNDArray();    // -> NumSharp, no manual UnmanagedMemoryBlock
       Console.WriteLine(nd);             // [0 1 2 3]
   }

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

   NDArrayPythonInterop.RegisterCodec();   // once per process
   
   using (Py.GIL())
   {
       dynamic np_ = Py.Import("numpy");
       PyObject npArr = np_.arange(4);
   
       NDArray nd = npArr.As<NDArray>();   // implicit decode via the codec
       Console.WriteLine(nd);              // [0 1 2 3]
   }

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

   closed this as completedon Sep 7, 2026