Question

Main program:

player = Player("player.png",[10,650])
players = pygame.sprite.Group()
players.add(player)

while True:
    for event in pygame.event.get():
      if event.type == KEYDOWN:
        if event.key == K_RIGHT:
          player.goright()
        if event.key == K_LEFT:
          player.goleft()           
      if event.type == KEYUP:
        if event.key == K_RIGHT:
          player.cangoright = False
        if event.key == K_LEFT:
          player.cangoleft = False

players.update()
players.draw(SCREEN)
pygame.display.update()
clock.tick(FPS)

The relevant sprite’s functions:

def update(self):
  if self.cangoright:
    self.rect.left += self.speed
  if self.cangoleft:
    self.rect.left -= self.speed

def goright(self):               
  if self.rect.right <= 1024:
    self.cangoright = True
  else:
    self.cangoright = False

def goleft(self):             
  if self.rect.left >= 0:
    self.cangoleft = True
  else:
    self.cangoleft = False

The problem is that the “cangoright” and “cangoleft” flags don’t seem to be working properly. When the sprite has surpassed the edges of the screen (0 on the left and 1024 on the right), the flags should be set to false, and thus the ifs in the update function should return false, but this doesn’t happen.

Answer 1

I believe part of the problem is that you’re only updating left in self.rect. Try updating both left and right instead, and see if that changes things.

More importantly, this code is a bit hard to read, and too complex what you’re trying to do. You might be better served by checking the bounds of the screen in your update function instead of in your key event handler. In reality this is part of the physics of your game, so it should probably be hung off of there.

In other words, use the event loop to set flags which express the intention of the player to the update function. Use the update function to apply the rules of the game (physics, etc) to the game state based on the flags set by the event loop.

Maybe something like this?

while True:
  ...
    for event in pygame.event.get():
      if event.type == KEYDOWN:
        if event.key == K_RIGHT:
          player.goright = True
        if event.key == K_LEFT:
          player.goleft = True
      if event.type == KEYUP:
        if event.key == K_RIGHT:
          player.goright = False
        if event.key == K_LEFT:
          player.goleft = False

  players.update()
  players.draw(SCREEN)
  pygame.display.update()
  clock.tick(FPS)

def update(self):
  if self.goright and self.speed < SPEED_MAX:
    self.speed += ACCEL_INCREMENT
  if self.goright and self.speed > -SPEED_MAX:
    self.speed -= ACCEL_INCREMENT

  new_left_pos = self.rect.left + self.speed
  new_right_pos = self.rect.right + self.speed

  if new_left_pos > 0 and new_right_pos < 1024:
        self.rect.left += self.speed
        self.rect.right += self.speed