How To Fix Pygame.PixelArray IndexError: Invalid Index Error

I create a pygame.PixelArray object uses the pygame main screen window surface object ( returned by the method pygame.display.set_mode() ), and when I assign color to each item of the pygame.PixelArray object in a loop it throws the error pygame.PixelArray IndexError: invalid index. This article will tell you how to fix it.

1. How To Reproduce The Error pygame.PixelArray IndexError: invalid index.

1. Create the pygame main window surface object using the pygame.display.set_mode() method.

   MAIN_WINDOW_SURFACE = pygame.display.set_mode((1000, 1000), pygame.RESIZABLE)

2. Create the pygame.PixelArray object with the above pygame main window surface object like below.

   pixel_array_obj = pygame.PixelArray(MAIN_WINDOW_SURFACE)

3. Create a list to save each pixel coordinate, each list item is another list that contains only 2 numbers( pixel X coordinate & pixel Y coordinate).

   def build_random_number_pair_list():
       
       ret_list = []
       
       # the main window surface width is 1000. 
       x_number_list = list(range(0, 1000))
       # the main window surface height is 1000.
       y_number_list = list(range(0, 1000))
       
       x_number_list_len = len(x_number_list)
       
       for i in range(x_number_list_len):
           
           x = random.choice(x_number_list)
           
           y = random.choice(y_number_list)
       
           pair_list = [x, y]
           
           ret_list.append(pair_list)
        
       return ret_list

4. Loop in the returned list above, and assign a color to each of the pixels in the pygame.PixelArray object.

   pixels_list = build_random_number_pair_list()
          
   for pixel in pixels_list:
           
       color = get_random_color()
       
       pixel_array_obj[pixel[0], pixel[1]] = color

5. The error occurred at the assigning color line, below is the error message.

   pixel_array_obj[pixel[0], pixel[1]] = color
   ......
   IndexError: invalid index

2. How To Fix The Error pygame.PixelArray IndexError: invalid index.

1. The reason for this error is the pygame.PixelArray object’s shape is smaller than the pixel coordinate that is saved in the pixel coordinate list object ( pixels_list ).
2. We can get the pygame.PixelArray object’s shape using the below code.

   print('pixel_array_obj.shape = ', pixel_array_obj.shape)
   
   # below is the above code output in the console.
   pixel_array_obj.shape =  (1000, 963)
   

3. The pygame.PixelArray object’s shape is decided by the main window surface object’s shape, we can see this using the below source code.

   print('MAIN_WINDOW_SURFACE.get_size = ', MAIN_WINDOW_SURFACE.get_size())
           
   print('MAIN_WINDOW_SURFACE.get_width = ', MAIN_WINDOW_SURFACE.get_width())
           
   print('MAIN_WINDOW_SURFACE.get_height = ', MAIN_WINDOW_SURFACE.get_height())
   
   # below is the above source code output.
   MAIN_WINDOW_SURFACE.get_size =  (1000, 963)
   MAIN_WINDOW_SURFACE.get_width =  1000
   MAIN_WINDOW_SURFACE.get_height =  963

4. So we should change the code in the build_random_number_pair_list() method like below.

   def build_random_number_pair_list():
       
       ret_list = []
         
       x_number_list = list(range(0, MAIN_WINDOW_SURFACE.get_width()))
       
       y_number_list = list(range(0, MAIN_WINDOW_SURFACE.get_height()))
       
       x_number_list_len = len(x_number_list)
       
       for i in range(x_number_list_len):
           
           x = random.choice(x_number_list)
           
           y = random.choice(y_number_list)
       
           pair_list = [x, y]
           
           ret_list.append(pair_list)
        
       return ret_list

5. Then the pixel’s coordinate x, y value will be limited to the main window screen surface pixel number range, and then the error will not happen again.
6. I also found that if you do not pass the argument pygame.RESIZABLE to the method pygame.display.set_mode(), then the main window surface object’s width & height value will be the same as the first window size tuple argument.

   # when you do not pass the pygame.RESIZABLE argument.
   MAIN_WINDOW_SURFACE = pygame.display.set_mode((1000, 1000))
   
   # the pygame main window's size will like below.
   MAIN_WINDOW_SURFACE.get_size() =  (1000, 1000)

7. If you pass pygame.FULLSCREEN to create the pygame main window, the returned window size should be your computer’s screen resolution.

   pygame.display.set_mode((1000, 1000), pygame.FULLSCREEN)
   
   MAIN_WINDOW_SURFACE.get_size() = (1280, 1024)

8. Below are the window pixel shapes that are generated by other window modes.

   MAIN_WINDOW_SURFACE = pygame.display.set_mode((1000, 1000), pygame.NOFRAME)
   
   MAIN_WINDOW_SURFACE.get_size() =  (1000, 1000)
   
   ****************************************************************************************
   MAIN_WINDOW_SURFACE = pygame.display.set_mode((1000, 1000), pygame.DOUBLEBUF)
   
   MAIN_WINDOW_SURFACE.get_size() =  (1000, 1000)
   
   ****************************************************************************************
   MAIN_WINDOW_SURFACE = pygame.display.set_mode((1000, 1000), pygame.HWSURFACE)
   
   MAIN_WINDOW_SURFACE.get_size() =  (1000, 1000)
   
   ****************************************************************************************
   MAIN_WINDOW_SURFACE = pygame.display.set_mode((1000, 1000), pygame.SCALED)
   
   MAIN_WINDOW_SURFACE.get_size() =  (1000, 1000)
   
   ****************************************************************************************
   MAIN_WINDOW_SURFACE = pygame.display.set_mode((1000, 1000), pygame.SHOWN)
   
   MAIN_WINDOW_SURFACE.get_size() =  (1000, 1000)
   
   ****************************************************************************************
   MAIN_WINDOW_SURFACE = pygame.display.set_mode((1000, 1000), pygame.HIDDEN)
   
   MAIN_WINDOW_SURFACE.get_size() =  (1000, 1000)