ship.py

import pygame
from pygame.sprite import Sprite

class Ship(Sprite):

	def __init__(self, bs_settings, screen):
		"""Initialize the ship and set its starting position.""" 
		super(Ship, self).__init__()
		self.screen = screen
		self.bs_settings = bs_settings
		# Load the ship image and get its rect.
		self.image = pygame.image.load('images/osh.bmp')
		self.rect = self.image.get_rect()
		self.screen_rect = screen.get_rect()

		# Start each new ship at the bottom center of the screen.
		self.rect.centerx = self.screen_rect.centerx
		self.rect.bottom = self.screen_rect.bottom

		# Store a decimal value for the ship's center. 
		self.centerx = float(self.rect.centerx)
		self.centery = float(self.rect.centery)
			
		# Set movement flags.
		self.moving_right = False
		self.moving_left = False
		self.moving_up = False
		self.moving_down = False

	def center_ship(self):
		"""Center the ship on the screen."""
		self.center = self.screen_rect.centerx
		self.center = self.screen_rect.centery

	def update(self):
		"""Update the ship's position based on movement flags."""
		# Update the ship's center, not the rect. 
		if self.moving_right and self.rect.right < self.screen_rect.right:
			self.centerx += self.bs_settings.ship_speed_factor
		if self.moving_left and self.rect.left > 0:
			self.centerx -= self.bs_settings.ship_speed_factor
		
		if self.moving_up and self.rect.top > 0:
			self.centery -= self.bs_settings.ship_speed_factor
		if self.moving_down and self.rect.bottom < self.screen_rect.bottom:
			self.centery += self.bs_settings.ship_speed_factor

		# Update rect object from self.center
		self.rect.centerx = self.centerx
		self.rect.centery = self.centery	

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