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Boost::Python Help

Started by slynk Sep 26, 2011 at 3:02 PM 2 replies 2.2k views

Original Post

Sep 26, 2011 at 3:02 PM

I'm desperately trying to expose an instantiated class object to python so that it can access its public functions to initialize it. For example, I instantiated an sMainMenu object menu. I call my python wrapper's Expose_MainMenu(menu); function:


 
 void PythonWrapper::Expose_MainMenu(sMainMenu &menu)
 {
 try{
 main_namespace["sMainMenu"] = boost::python::class_<sMainMenu>("sMainMenu")
 .def("LoadImage",&sMainMenu::LoadImage)
 .def("LoadSprite", &sMainMenu::LoadSprite)
 .def("LoadButton",&sMainMenu::LoadButton);
 
 main_namespace["menu"] = boost::python::ptr(&menu);
 }
 catch(boost::python::error_already_set const &){
 std::string perror_str = parse_python_exception();
 std::cout << "Error in Python: " << perror_str << std::endl;
 }
 }

Now in my python exposure of sMainMenu, I've only defined the functions I want python scripts to have access to... is this a mistake? Is this the reason my application either doesn't do anything or completely crashes? Do I need to define the class with every function and member of the class?

I know if I call the function twice, it'll crash from the double definition of sMainMenu (I'm going to pull it out into a module once it works.) The script is being "executed" by calling:


 
 void PythonWrapper::Execute_Script()
 {
 try{
 PyRun_String("import Main_Menu", Py_file_input, main_namespace.ptr(), main_namespace.ptr());
 }
 catch(boost::python::error_already_set const &){
 std::string perror_str = parse_python_exception();
 std::cout << "Error in Python: " << perror_str << std::endl;
 }
 }

I placed some prints through out the script but only the first one outputs to the command prompt. My script is:


 
 print("Loaded the file...\n")
 
 menu.LoadImage("resources/texture/background.png"); 
 menu.LoadImage("resources/texture/biNewGame.png"); 
 menu.LoadImage("resources/texture/baNewGame.png"); 
 menu.LoadImage("resources/texture/biLoadGame.png"); 
 menu.LoadImage("resources/texture/baLoadGame.png"); 
 menu.LoadImage("resources/texture/biOptions.png"); 
 menu.LoadImage("resources/texture/baOptions.png"); 
 menu.LoadImage("resources/texture/biQuit.png"); 
 menu.LoadImage("resources/texture/baQuit.png"); 
 print("Loaded the images...\n")
 
 menu.LoadSprite(0, 0, 0);
 print("Loaded the background...\n")
 
 
 menu.LoadButton(1, 2, 350, 174);
 menu.LoadButton(3, 4, 333, 328);
 menu.LoadButton(5, 6, 398, 483);
 menu.LoadButton(7, 8, 455, 640);
 print("Loaded the buttons...\n")

If I try to use boost::python::exec_file() the game crashes, hence the use instead of PyRun_String()

slynk

Sep 27, 2011 at 5:30 PM

I placed a cout at the beginning of the LoadImage function and it's not even called. Has to be an issue with my class or object exposure to python.

slynk

Sep 27, 2011 at 6:29 PM

Alright I switched from an import to the boost::python::exec_file() method. It was crashing because I passed the pile name with the .py extension, when I removed it, it threw an error message before crashing:


 
 Error in Python: <class 'SyntaxError'>: ('invalid character in identifier', ('Ma
 in_Menu', 1, 3, '?????????\x04x\x18???\x04????????????'))
 
 This application has requested the Runtime to terminate it in an unusual way.
 Please contact the application's support team for more information.
 
 Process returned 3 (0x3) execution time : 98.969 s
 Press any key to continue.

Any help?

slynk

Sep 27, 2011 at 8:16 PM

I think it may be due to inheritance issues as sMainMenu is derived of sMenu which is derived of GameState... I'm not really sure how to wrap it all up:

GameState:


 
 class GameState
 {
 public:
 virtual const void Init(GameStateManager* g) = 0;
 virtual const void Cleanup() = 0;
 
 virtual const void Pause() = 0;
 virtual const void Resume() = 0;
 
 virtual const void HandleEvents() = 0;
 virtual const void Update() = 0;
 virtual const void Draw(sf::RenderWindow* window) = 0;
 
 void ChangeState(GameState* state);
 
 /// Utility functions for Python mostly
 void LoadImage(std::string path);
 void LoadSprite(int textureNum, int x, int y);
 
 protected:
 std::vector<sf::Texture> textures;
 std::vector<sf::Sprite> sprites;
 std::vector<sf::Text> text;
 GameStateManager* game;
 bool isPaused;
 
 };

sMenu:


 
 class sMenu : public GameState
 {
 public:
 virtual const void Init(GameStateManager* g);
 const void Cleanup();
 
 const void Pause(){isPaused = true;}
 const void Resume(){isPaused = false;}
 
 const void HandleEvents();
 const void Update();
 const void Draw(sf::RenderWindow* window);
 
 ///Utility functions mostly for Python
 void LoadButton(int textureI, int textureA, int x, int y);
 
 protected:
 std::vector<Button> buttons;
 int selected;
 virtual const void toDo(int which) = 0;
 };

sMainMenu:


 
 class sMainMenu : public sMenu
 {
 public:
 virtual const void Init(GameStateManager* g);
 
 const void toDo(int which);
 };

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