this code is in my main game loop
key = pygame.key.get_pressed() #create a key index
if K_UP in key: #check if the up arrow is pressed
redcar.speed = (0, -2)
else:
redcar.speed = (0, 0)
redcar.rect = redcar.rect.move(redcar.speed) #move redcar by speed
but pressing the up arrow doesn't move the sprite.