alien.py

import pygame
from pygame.sprite import Sprite

class Alien(Sprite):
    """the class to represent single slien in a fleet"""
    def __init__(self, ai_settings, screen):
        """Initiaze the game and set its starting possition"""
        super(Alien,self).__init__()
        self.screen=screen
        self.ai_settings=ai_settings
        
        """load the the image"""
        self.image=pygame.image.load('images/alien.bmp')
        self.rect=self.image.get_rect()
        
        self.rect.x=self.rect.width
        self.rect.y=self.rect.height
        
        self.x=float(self.rect.x)
        
    def blitme(self):
        """draw the allien at its current location"""
        self.screen.blit(self.image,self.rect)
        
    def check_edges(self):
        """return true if elien is at the adge of the screen"""
        screen_rect=self.screen.get_rect()
        if self.rect.right>=screen_rect.right:
            return True
        elif self.rect.left<=0:
            return True
        
    
    def update(self):
        """move the alien right"""
        self.x+=(self.ai_settings.alien_speed_factor*self.ai_settings.fleet_direction)
        self.rect.x=self.x