Detecting if two sprites overlap using PyGame

Question

I am trying to make my own game and i need to know when two sprites overlap and if they overlap then the game will load in a new picture using win.blit I have tried looking at other peoples posts but they didnt help me at all. I am new, please give an in-depth explanation

EDIT: Please make it as short as possible

EDIT 2 (about 2 years later): Sorry for making such a shit question lol

Answer 1

As short as possible.

if ( sprite1.rect.colliderect( sprite2.rect ) ):
    # TODO handle collision

But for a more useful example...

Create a global sprite group. The sprite group allows the code to do a simple check for collisions on the whole group at once. Maybe two groups could be useful, e.g.: aliens and bullets, biscuits and dips.

SPRITES = pygame.sprite.Group()

Define a sprite. The sprite's update() function is called each frame to do everything the sprite needs to do inter-frame. This might be move, change the bitmap (for animation), or check for collisions, etc. This sprite has a name so we can print out who collides with whom.

class RockSprite(pygame.sprite.Sprite):
    def __init__(self, name, image, position):
        pygame.sprite.Sprite.__init__(self)
        self.name         = name
        self.image        = image
        self.rect         = self.image.get_rect()
        self.rect.center  = position

    def update(self):
        # Move the sprite
        # ... TODO
        # Have we collided with any sprite?
        hit_by = pygame.sprite.spritecollide( self, SPRITES, False )
        hit_by.remove( self ) # other than ourselves
        for other_sprite in hit_by:
            print( "Sprite [%s] collided with [%s]" % ( self.name, other_sprite.name ) )

Create a bunch of sprites. This shows how to create an instance of a RockSprite, and add it to the SPRITE group.

# Make some sprites, including two that overlap (but it depends on the .png size)
sprite_image = pygame.image.load("rock.png").convert_alpha()
rock_01 = RockSprite( "rock01", sprite_image, (10, 10) )
rock_02 = RockSprite( "rock02", sprite_image, (15, 15) )
rock_03 = RockSprite( "rock03", sprite_image, (50, 50) )
# Add them to the global SPRITE group
SPRITES.add(rock_01)        
SPRITES.add(rock_02)
SPRITES.add(rock_03)

Be sure to call the sprite group update() function in the main loop:

while not done:

    # Move the sprites (and checks for collisions) - calls update() on each member
    SPRITES.update()

    # paint he screen
    # handle user input  
    ...

Which gives the full demonstration code:

import pygame
WINDOW_WIDTH=400
WINDOW_HEIGHT=400

pygame.init()
WINDOW  = pygame.display.set_mode((WINDOW_WIDTH, WINDOW_HEIGHT))
SPRITES = pygame.sprite.Group()

class RockSprite(pygame.sprite.Sprite):
    def __init__(self, name, image, position):
        pygame.sprite.Sprite.__init__(self)
        self.name         = name
        self.image        = image
        self.rect         = self.image.get_rect()
        self.rect.center  = position

    def update(self):
        # Move the sprite
        # ... TODO
        # Have we collided with any sprite?
        hit_by = pygame.sprite.spritecollide( self, SPRITES, False )
        hit_by.remove( self ) # other than ourselves
        for other_sprite in hit_by:
            print( "Sprite [%s] collided with [%s]" % ( self.name, other_sprite.name ) )


# Make some sprites, including two that overlap
sprite_image = pygame.image.load("rock.png").convert_alpha()
rock_01 = RockSprite( "rock01", sprite_image, (10, 10) )
rock_02 = RockSprite( "rock02", sprite_image, (15, 15) )
rock_03 = RockSprite( "rock03", sprite_image, (90, 90) )
# Add them to the global SPRITE group
SPRITES.add(rock_01)
SPRITES.add(rock_02)
SPRITES.add(rock_03)

clock = pygame.time.Clock()
done = False
while not done:

    # Move the sprites (and checks for collisions)
    SPRITES.update()

    # Paint the screen
    WINDOW.fill( ( 0,0,0 ) )
    SPRITES.draw( WINDOW )
    pygame.display.update()
    pygame.display.flip()

    # Check for user-events
    for event in pygame.event.get():
        if (event.type == pygame.QUIT):
            done = True

    clock.tick_busy_loop(60)