Why "sys.prefix", "sys.exec_prefix" is None? #1757

  // myapp.exe
  static void Main(string[] args)
  {
      Environment.SetEnvironmentVariable("PYTHONNET_PYDLL", @"C:/Users/xxx/AppData/Local/Programs/Python/Python38/python38.dll", EnvironmentVariableTarget.Process);
      string[] pathes = {
          PythonEngine.PythonPath,
          Path.GetFullPath("./pysrc"), //script location
      };
      PythonEngine.PythonPath = string.Join(Path.PathSeparator.ToString(), pathes);
      //PythonEngine.PythonHome = @"C:/Users/xxx/AppData/Local/Programs/Python/Python38";

      PythonEngine.Initialize();
      using (Py.GIL())
      {
          PythonEngine.Exec("import myscript");
      }
    PythonEngine.Shutdown();
  }