Pygame image moves but image rectangle does not [duplicate] - python-3.x

Question

My collide_rect function isn't working properly. It always returns True, when it's not suppose to. I have tried looking on the internet but nothing is working for me. I think the collide rect somehow did not use the actual coordinates for the two sprites. Can anyone help with this?
import pygame
import pygame.sprite
import sys
gameDisplay = pygame.display.set_mode((800,600))
pygame.display.set_caption("test_collision")
clock = pygame.time.Clock()
crashed = False
class Ball(pygame.sprite.Sprite):
def __init__(self):
pygame.sprite.Sprite.__init__(self)
self.image = pygame.image.load("ball.png")
self.rect = self.image.get_rect()
self.x = 280
self.y = 475
self.col = False
def update(self):
gameDisplay.blit(self.image, (self.x,self.y))
self.rect = self.image.get_rect()
def test_collisions(self,sprite):
self.col = pygame.sprite.collide_rect(self,sprite)
class Obstacle(pygame.sprite.Sprite):
def __init__(self):
pygame.sprite.Sprite.__init__(self)
self.x = 1000
self.y = 483
self.image = pygame.image.load("obstacle.png")
self.time = pygame.time.get_ticks()
self.rect = self.image.get_rect()
def change_x(self):
self.time = pygame.time.get_ticks()
self.x = -(self.time/5) + 800
def update(self):
self.rect = self.image.get_rect()
gameDisplay.blit(self.image,(self.x,self.y))
obstacle = Obstacle()
ball = Ball()
while not crashed:
for event in pygame.event.get():
if event.type == pygame.QUIT:
crashed = True
gameDisplay.fill((255,255,255))
ball.update()
obstacle.change_x()
obstacle.update()
ball.test_collisions(obstacle)
if ball.col:
print("colided")
pygame.display.flip()
clock.tick(1000)
pygame.quit()
sys.exit()
P.S This is my first post :)

Answer 1

pygame.Surface.get_rect.get_rect() returns a rectangle with the size of the Surface object, but it returns a rectangle that always starts at (0, 0) since a Surface object has no position.
The Surface is placed at a position on the display with the blit function.
You've to set the location of the rectangle, either by a keyword argument, e.g:
self.rect = self.image.get_rect(topleft = (self.x, self.y))
or an assignment to a virtual attribute (see pygame.Rect), e.g:
self.rect = self.image.get_rect()
self.rect.topleft = (self.x, self.y)
It is absolutely unnecessary to add some extra attributes self.x and self.y. Use the location of the rectangle instead. e.g:
class Ball(pygame.sprite.Sprite):
def __init__(self):
pygame.sprite.Sprite.__init__(self)
self.image = pygame.image.load("ball.png")
self.rect = self.image.get_rect(topleft = (280, 475))
self.col = False
def update(self):
gameDisplay.blit(self.image, self.rect)
def test_collisions(self,sprite):
self.col = pygame.sprite.collide_rect(self,sprite)
class Obstacle(pygame.sprite.Sprite):
def __init__(self):
pygame.sprite.Sprite.__init__(self)
self.image = pygame.image.load("obstacle.png")
self.time = pygame.time.get_ticks()
self.rect = self.image.get_rect(topleft = (1000, 483))
def change_x(self):
self.time = pygame.time.get_ticks()
self.rect.x = -(self.time/5) + 800
def update(self):
gameDisplay.blit(self.image, self.rect)
Further note, that you can get rid of the methods Ball.update() respectively Obstacle.update() (you can delete them), if you use a pygame.sprite.Group and call .draw(), which uses the .image and .rect properties of the contained sprites, to draw them. e.g.:
obstacle = Obstacle()
ball = Ball()
all_sprites = pygame.sprite.Group([obstacle, ball])
while not crashed:
# [...]
gameDisplay.fill((255,255,255))
all_sprites.draw(gameDisplay)
pygame.display.flip()
clock.tick(1000)