ship.py

import pygame
from pygame.sprite import Sprite

class Ship(Sprite):
    # a class to manage the ship

    def __init__(self, ai_game):
        #initilize the ship and set its starting position
        super().__init__()
        self.screen = ai_game.screen
        self.settings = ai_game.settings
        self.screen_rect = ai_game.screen.get_rect()

        #load the ship image and get its rect
        self.image = pygame.image.load('image/plan.bmp')
        self.rect = self.image.get_rect()

        #start each new ship at the bottom center of the screen.
        self.rect.midbottom = self.screen_rect.midbottom

        #store a decimal value for the ship's horizontal position.
        self.x = float(self.rect.x)

        #movement flag
        self.moving_right = False
        self.moving_left = False

    def update(self):
        # update the ship's position based on movement flag.
        # update the ship's x value, not the rect.
        if self.moving_right and self.rect.right < self.screen_rect.right:
            self.x += self.settings.ship_speed
        if self.moving_left and self.rect.left > 0:
            self.x -= self.settings.ship_speed

        #update rect object from self.x.
        self.rect.x = self.x

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

    def center_ship(self):
        # center the ship on the screen.
        self.rect.midbottom = self.screen_rect.midbottom
        self.x = float(self.rect.x)