alien.py

import pygame

# --------------------------------
from pygame.sprite import Sprite
# --------------------------------


class Alien(Sprite):
    '''A class that represents a single alien in the fleet.'''

    def __init__(self, ai_settings, screen):
        '''Initializes the alien and sets its starting position.'''
        super().__init__()
        self.screen = screen
        self.ai_settings = ai_settings

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

        # Start each new alien near the top left of the screen
        self.rect.x = self.rect.width
        self.rect.y = self.rect.height

        # Store the exact position of the alien
        self.x = float(self.rect.x)

    def blitme(self):
        '''Draw the alien in its current position.'''
        self.screen.blit(self.image, self.rect)

    def check_edges(self):
        '''Returns True if the alien is at the edge 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 left or right.'''
        self.x += (self.ai_settings.alien_speed_factor *
                   self.ai_settings.fleet_direction)
        self.rect.x = self.x