Question

I found a solution to make a sprite move when you hold a key down. The problem is that it forces writing ugly duplicated code. The current solution I found is:

       for event in pygame.event.get():
            if event.type == KEYDOWN:
                keystate = pygame.key.get_pressed()
                while keystate[K_RIGHT]:
                    screen.fill((255,255,255))
                    pygame.event.get()

                    for sprite in sprites:
                        rimage = sprite[1].getimage()

                        if sprite[2] is None:
                            x+=3
                            sprite[1].update(time)
                            screen.blit(rimage, (x,y))
                            if sprite[1].isfinished() == True:
                                sprite[1].reset()
                            last_dir = "right"
                            if x >= screen_width - rimage.get_width():
                                x = screen_width - rimage.get_width()

                    #update player sprite movement
                    #update player sprite animation
                    #update rest of game map

                    keystate = pygame.key.get_pressed()
                    time = pygame.time.get_ticks()


                    pygame.display.update()

The problem is that the while keystate block. It has to be repeated for each direction and the game world needs to be updated in each while block. That is five places where the same code needs to be duplicated….4 directions plus if a key is not pressed. I could wrap it in a function but I was wondering if there was a better way to handle holding down a button in pygame.

Answer 1

The usual way program in pygame is use the events to update the direction, then write the update position code outside events, that way you don’t need replicated code.

clock = pygame.time.Clock()

direction = (0,0)

while True:    # main loop

   for event in pygame.event.get():

        if event.type == KEYDOWN:
            if event.key == K_RIGHT:
                direction = (3, 0)
            elif event.key == K_LEFT:
                direction = (-3, 0)
            elif event.key == K_UP:
                direction = (0, 3)
            elif event.key == K_DOWN:
                direction = (0, -3)
            else:
                print "Unrecognized key"

        if event.type == KEYUP:
            direction = (0, 0)

    screen.fill((255,255,255))

    for sprite in sprites:
        rimage = sprite[1].getimage()

        if sprite[2] is None:

            # Check if new position is inside the screen
            new_pos = x + direction[0], y + direction[1]
            if new_pos[0] + rimage.get_width() < screen_width:
                x = new_pos[0]
            if new_pos[1] + rimage.get_height() < screen_height:
                y = new_pos[1]

            # Draw the sprite
            sprite[1].update(time)
            screen.blit(rimage, (x,y))
            if sprite[1].isfinished() == True:
                sprite[1].reset()
                last_dir = direction

    #update player sprite movement
    #update player sprite animation
    #update rest of game map

    time = pygame.time.get_ticks()

    pygame.display.update()

    clock.tick(40)  # Keep game running at 40 fps

If you want you can achieve the same with keystate, in such case you don’t need to process key events.