alien.py

# -*- coding: utf-8 -*-
import pygame
from pygame.sprite import Sprite

class Alien(Sprite):
# A class to represent a single alien in the fleet.
	
	def __init__(self, ai_settings, screen):
		# Initialize the alien and set its starting position.
		super(Alien, self).__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.image = pygame.transform.scale(self.image, (50,50))
		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 alien's exact position.
		self.x = float(self.rect.x)

	def blitme(self):
		# Draw the alien at its current location.
		self.screen.blit(self.image, self.rect)

	def check_edges(self):
		# Return True if alien is at edge of 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):
		# # alien exact position by self.x
		# 	self.x += self.ai_settings.alien_speed_factor
		# Move the alien right or left.
		self.x += (self.ai_settings.alien_speed_factor *self.ai_settings.fleet_direction)
		self.rect.x = self.x