pythonnet 3.0.0.post1

Calling .NET code from Python

Python.NET allows CLR namespaces to be treated essentially as Python packages.

import clr
from System import String
from System.Collections import *

To load an assembly, use the AddReference function in the clr module:

import clr
clr.AddReference("System.Windows.Forms")
from System.Windows.Forms import Form

By default, Mono will be used on Linux and macOS, .NET Framework on Windows. For details on the loading of different runtimes, please refer to the documentation.

from pythonnet import load
load("coreclr")

import clr

Embedding Python in .NET

• You must set Runtime.PythonDLL property or PYTHONNET_PYDLL environment variable starting with version 3.0, otherwise you will receive BadPythonDllException (internal, derived from MissingMethodException) upon calling Initialize. Typical values are python38.dll (Windows), libpython3.8.dylib (Mac), libpython3.8.so (most other Unix-like operating systems).

• Then call PythonEngine.Initialize(). If you plan to use Python objects from multiple threads, also call PythonEngine.BeginAllowThreads().

• All calls to python should be inside a using (Py.GIL()) {/* Your code here */} block.

• Import python modules using dynamic mod = Py.Import("mod"), then you can call functions as normal, eg mod.func(args).

• Use mod.func(args, Py.kw("keywordargname", keywordargvalue)) or mod.func(args, keywordargname: keywordargvalue) to apply keyword arguments.

• All python objects should be declared as dynamic type.

• Mathematical operations involving python and literal/managed types must have the python object first, eg. np.pi * 2 works, 2 * np.pi doesn’t.

static void Main(string[] args)
{
    PythonEngine.Initialize();
    using (Py.GIL())
    {
        dynamic np = Py.Import("numpy");
        Console.WriteLine(np.cos(np.pi * 2));

        dynamic sin = np.sin;
        Console.WriteLine(sin(5));

        double c = (double)(np.cos(5) + sin(5));
        Console.WriteLine(c);

        dynamic a = np.array(new List<float> { 1, 2, 3 });
        Console.WriteLine(a.dtype);

        dynamic b = np.array(new List<float> { 6, 5, 4 }, dtype: np.int32);
        Console.WriteLine(b.dtype);

        Console.WriteLine(a * b);
        Console.ReadKey();
    }
}

1.0
-0.958924274663
-0.6752620892
float64
int32
[  6.  10.  12.]

Resources

Information on installation, FAQ, troubleshooting, debugging, and projects using pythonnet can be found in the Wiki:

https://github.com/pythonnet/pythonnet/wiki

Mailing list

https://mail.python.org/mailman/listinfo/pythondotnet

Chat

https://gitter.im/pythonnet/pythonnet

.NET Foundation

This project is supported by the .NET Foundation.