alien.py

import pygame
from pygame.sprite import Sprite

class Alien(Sprite):
    """ A class to represent a single alien in the fleet. """ 
    
    def __init__(self, ai_game):
        """ INitialize the alien abd set its rect starting position. """ 

        super().__init__()
        self.screen = ai_game.screen
        self.settings = ai_game.settings

        #load the alien image and set its rect attribute. 
        self.image = pygame.image.load('images/space1.bmp')
        self.rect = self.image.get_rect()

        #start each new alien near the top ;eft of screen. 
        self.rect.x = self.rect.width
        self.rect.y = self.rect.height

        #store the aliens exact horizontal position. 
        self.x = float(self.rect.x)


    def check_edges(self):
        """ Return tue if alie is at edge of screen . """ 
        screen_rect = self.screen.get_rect()
        if self.rect.right >= screen_rect.right or self.rect.left <= 0 :
            return True


    def update(self):
        """ Move the alien to the right or left. """
        self.x += (self.settings.alien_speed * self.settings.fleet_direction)
        self.rect.x = self.x