How do you make a Sprite blitting twice have two separate collision boxes in Pygame?

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I don't know if my title was very clear, so I'm going to try to explain this more clearly here. So I have a Sprite in Pygame called spikes. I want there to be more than one spikes so I blit a second one. Problem is, my spike_collision box only works on the first one that I blit, and not the second one. Other than having to make a second collision box, how can I have the second spikes to have its own collision box as well?

Here's the blit code:

        screen.blit(spikes, (spike_x, 500 - player_y + 476))
        screen.blit(spikes, (spike_x + 200, 500 - player_y + 476))

Here's the collision-box code:

spike_collision = spikes.get_rect(topleft=(spike_x, 500 - player_y + 476))

Thanks.

blit collision-detection collision pygame python
1 Answers

I'm assuming when you write "sprite", you mean a bitmap-sprite, and not a pygame.sprite.Sprite.

It's probably best to maintain a sprite as a bitmap and a rectangle, then always draw the sprite at its rectangle, adjusting the rectangle to re-position the sprite, and using it for any collisions.

This could easily be done with list-pairs:

spike_image = pygame.image.load('spikes.png').convert_alpha()
spike_rect  = spike_image.get_rect( )
spikes_a = [ spike_image, spike_rect( top_left=( 100, 100 ) )
spikes_b = [ spike_image, spike_rect( top_left=( 200, 200 ) )

# ...

screen.blit( spikes_a[0], spikes_a[1] )
screen.blit( spikes_b[0], spikes_b[1] )
# etc.

if ( spikes_a[1].colliderect( player_rect ) ):
    print( "ouch!" )

However, it would behoove you to use a "proper" sprite object. Sure there's a bit of extra set-up, but it's repaid multiple times with ease of use:

class Spike( pygame.sprite.Sprite ):
    def __init__( self, position=( 0, 0 ) ):
        self.image = pygame.image.load('spikes.png').convert_alpha()
        self.rect  = self.image.get_rect( top_left = position )

    def moveTo( self, position ):
        self.rect  = self.image.get_rect( top_left = position )

    def moveBy( self, dx, dy ):
        self.rect.move_ip( dx, dy )


spike_a = Spike( ( 100, 100 ) )
spike_b = Spike( ( 200, 200 ) )

spike_a.draw( window )  # get this for free

There's a whole lot of useful group & collision functionality that comes along with using Sprite objects, it's well worth a read: https://www.pygame.org/docs/ref/sprite.html

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