ship.py

import pygame
from pygame.sprite import Sprite

class Ship(Sprite):
    def __init__(self,ai_settings,screen):
        super(Ship,self).__init__()
        self.screen=screen

        self.image=pygame.image.load(r'D:\projects\Alien invasion\images\ship.bmp')
        self.rect=self.image.get_rect()
        self.screen_rect=screen.get_rect()

        self.rect.centerx=self.screen_rect.centerx
        self.rect.bottom=self.screen_rect.bottom

        self.moving_right=False
        self.moving_left=False

        self.ai_settings=ai_settings
        self.center=float(self.rect.centerx)

    def update(self):
        if self.moving_right and self.rect.right < self.screen_rect.right:
            self.center+=self.ai_settings.ship_speed_factor
        if self.moving_left and self.rect.left > 0:
            self.center-=self.ai_settings.ship_speed_factor

        self.rect.centerx=self.center

    def blitme(self):
        self.screen.blit(self.image,self.rect)

    def center_ship(self):
        self.center=self.screen_rect.centerx