I’m making a simple python game and there are 3 py files: alien_invasion, settings, ship. I would like the image position to be at the middle bottom of screen every time the game starts. It works when code are like the following:
alien_invasion.py:
import sys import pygame from settings import Settings from ship import Ship class AlienInvasion: """Overall class to manage game assets and behaviour.""" def __init__(self): """Initialize the game, and create game resources.""" pygame.init() self.settings = Settings() self.screen = pygame.display.set_mode( (self.settings.screen_width, self.settings.screen_height), pygame.RESIZABLE) pygame.display.set_caption("Alien Invasion") self.ship = Ship(self) def run_game(self): """Start the main loop for the game.""" while True: self._check_events() self.ship.update() self._update_screen() def _check_events(self): """Respond to keypresses and mouse events.""" for event in pygame.event.get(): if event.type == pygame.QUIT: sys.exit() elif event.type == pygame.KEYDOWN: if event.key == pygame.K_RIGHT: self.ship.moving_right = True elif event.key == pygame.K_LEFT: self.ship.moving_left = True elif event.type == pygame.KEYUP: if event.key == pygame.K_RIGHT: self.ship.moving_right = False elif event.key == pygame.K_LEFT: self.ship.moving_left = False def _update_screen(self): """"Update images on the screen, and flip to the new screen.""" self.screen.fill(self.settings.bg_color) self.ship.blitme() pygame.display.flip() if __name__ == '__main__': # Make a game instance, and run the game. ai = AlienInvasion() ai.run_game()
ship.py:
import pygame class Ship: """A class to manage the ship.""" def __init__(self, ai_game): """Initialize the ship and set its starting position.""" self.screen = ai_game.screen self.screen_rect = ai_game.screen.get_rect() # Load ship image and get its rect. self.image = pygame.image.load('images/ship.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 # Movement flags self.moving_right = False self.moving_left = False def update(self): """"Update the ship's position based on the movement flags.""" if self.moving_right: self.rect.x += 1 if self.moving_left: self.rect.x -= 1 def blitme(self): """Draw the ship at its current location.""" self.screen.blit(self.image, self.rect)
settings.py:
class Settings: """A class to store all settings for Alien Invasion.""" def __init__(self): """Initialize the game's settings.""" # Screen settings self.screen_width = 1200 self.screen_height = 800 self.bg_color = (230, 230, 230)
Then I made changes to settings.py and ship.py to adjust the moving speed:
ship.py:
import pygame class Ship: """A class to manage the ship.""" def __init__(self, ai_game): """Initialize the ship and set its starting position.""" self.screen = ai_game.screen self.settings = ai_game.settings self.screen_rect = ai_game.screen.get_rect() # Load ship image and get its rect. self.image = pygame.image.load('images/ship.bmp') self.rect = self.image.get_rect() # Store a decimal value for the ship's horizontal position self.x = float(self.rect.x) # Start each new ship at the bottom center of the screen. self.rect.midbottom = self.screen_rect.midbottom # Movement flags self.moving_right = False self.moving_left = False def update(self): """"Update the ship's position based on the movement flags.""" ## Update the ship's x value, not the rect. if self.moving_right: self.x += self.settings.ship_speed if self.moving_left: 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)
settings.py:
class Settings: """A class to store all settings for Alien Invasion.""" def __init__(self): """Initialize the game's settings.""" # Screen settings self.screen_width = 1200 self.screen_height = 800 self.bg_color = (230, 230, 230) # Ship settings self.ship_speed = 1.5
Then when I run the alien_invasion code, the image starts showing up at the left bottom of screen when game starts, which is not what I want.
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Answer
You need to set self.x
after setting the location of self.rect
:
class Ship: """A class to manage the ship.""" def __init__(self, ai_game): # [...] self.rect = self.image.get_rect() # Store a decimal value for the ship's horizontal position # self.x = float(self.rect.x) <--- delete # Start each new ship at the bottom center of the screen. self.rect.midbottom = self.screen_rect.midbottom self.x = float(self.rect.x) # <--- insert # [...]