First steps with Python.NET

[Gintaras]

This class makes it simpler.
 

Code:

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// class "Pynet.cs"
/*/ nuget PyNet\PythonNet; /*/
using Python.Runtime;

/// <summary>
/// Initializes the Python engine, locks its global interpreter and adds scope.
/// Optionally adds Python code; then you can call functions etc.
/// When disposing, unlocks/disposes objects and shuts down the engine.
/// </summary>
public class Pynet : IDisposable {
    Py.GILState _gil;
    PyModule _m;
    bool _shutdown;
    
    /// <summary>
    /// Initializes the Python engine and optionally adds code.
    /// </summary>
    /// <param name="code">If not null/"", calls <b>PyModule.Exec</b>.</param>
    /// <param name="enablePrint">Redirect the output of the Python's print function to console. Default true.</param>
    public Pynet(string code = null, bool enablePrint = true) {
        if (!PythonEngine.IsInitialized) {
            if (Environment.GetEnvironmentVariable("PYTHONNET_PYDLL").NE()) Runtime.PythonDLL = @"C:\Program Files\Python311\python311.dll"; //edit this if need. Or set the environment variable.
            PythonEngine.Initialize();
            _shutdown = true;
            //process.thisProcessExit += _ => PythonEngine.Shutdown(); //does not work
        }
        _gil = Py.GIL();
        
        if (enablePrint) {
            Module.Exec("""
import sys

class NetConsole(object):
    def __init__(self, writeCallback):
        self.writeCallback = writeCallback

    def write(self, message):
        self.writeCallback(message)

    def flush(self):
        pass

def setConsoleOut(writeCallback):
    sys.stdout = NetConsole(writeCallback)
""");
            var writer = (string s) => { Console.Write(s); };
            Module.InvokeMethod("setConsoleOut", Python.Runtime.PyObject.FromManagedObject(writer));
        }
        
        if (!code.NE()) Module.Exec(code);
    }
    
    /// <summary>
    /// Unlocks/disposes Python objects and shuts down the engine.
    /// </summary>
    public void Dispose() {
        _m?.Dispose();
        _gil?.Dispose();
        if (_shutdown) {
            try { PythonEngine.Shutdown(); } //without this the process does not exit
            catch (System.Runtime.Serialization.SerializationException) { } //thrown when using enablePrint
        }
    }
    
    /// <summary>
    /// Gets the result of <b>Py.CreateScope</b>.
    /// You can assign it to a <c>dynamic</c> variable and call functions defined in your Python code.
    /// </summary>
    public PyModule Module => _m ??= Py.CreateScope();
}

Examples.
 

Code:

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// script "Pynet examples.cs"
/*/ c Pynet.cs; /*/
using Python.Runtime;

#if true

string code = """
def Multi(a1, a2):
    return a1 * a2

def JoinStr(a1, a2):
    return a1 + a2
""";
using var pyn = new Pynet(code);
dynamic m = pyn.Module;
double d1 = m.Multi(2, 3.5);
string s1 = m.JoinStr("joi", "ned");
print.it(d1, s1);

#elif !true

using var pyn = new Pynet();
dynamic mod = Py.Import("math");
print.it(mod.cos(mod.pi * 2));

#elif !true

using var pyn = new Pynet();
print.it(PythonEngine.Eval("3 + 4"));

#elif !true

string code = """
import ctypes
ctypes.windll.user32.MessageBoxW(0, "Text", "Title", 1)
""";
using var pyn = new Pynet();
PythonEngine.RunSimpleString(code);

#endif