import os.path
import pygame
from pygame.sprite import Sprite
from game_stats import GameStats
from settings import Settings
class Alien(Sprite):
"""A class to represent a single alien in a fleet."""
def __init__(self, ai_settings: Settings, screen: pygame.SurfaceType,
image_name='images/alien1.png'):
"""Initialize the alien and set its starting position."""
super().__init__()
self.screen = screen
self.ai_settings = ai_settings
self.screen_rect = screen.get_rect()
# Load the alien image and set its rect attribute.
fullname = os.path.join('.', image_name)
try:
self.image = pygame.image.load(fullname)
except pygame.error:
print('Cannot load image:', image_name)
raise SystemExit
self.image = pygame.transform.scale(self.image, ai_settings.alien_size)
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
self.x = float(self.rect.x)
self.y = float(self.rect.y)
self.drop_dist = self.y + self.ai_settings.alien_drop_dist
def blitme(self):
"""Draw the alien at its current position."""
self.screen.blit(self.image, self.rect)
def update(self, stats: GameStats):
"""Move the alien."""
self.x += self.ai_settings.alien_speed_factor_x * self.ai_settings.alien_direction_x * stats.time_passed
self.rect.x = self.x
if self.y > self.drop_dist:
self.drop_dist += self.ai_settings.alien_drop_dist
self.y += self.ai_settings.alien_speed_factor_y * self.ai_settings.alien_direction_y * stats.time_passed
self.rect.y = self.y
def check_edges(self, edge='both'):
"""Returns True if alien is at edge of screen."""
left_edge = self.rect.left <= self.screen_rect.left
right_edge = self.rect.right >= self.screen_rect.right
if edge == 'left':
return left_edge
elif edge == 'right':
return right_edge
else:
return left_edge or right_edge
