alien_invasion.py

import sys
import pygame
from ship import Ship
from settings import Settings
from bullet import Bullet


class AlienInvasion:
	"""Overall class to manage game assets and behavior."""

	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.display.set_caption("Alien Invasion")

		self.ship = Ship(self)
		self.bullets = pygame.sprite.Group()


	def run_game(self):
		"""Start the main loop for the game."""
		while True:
			# Wach for keyboard and mouse events.
			self._check_events()
			self.ship.update()
			self._update_bullets()
			self.bullets.update()

			# Get rid of bullets that have disappeared.
			for bullet in self.bullets.copy():
				if bullet.rect.bottom <= 0:
					self.bullets.remove(bullet)
			print(len(self.bullets))
			self._update_screen()

			# Redraw the scree during each pass through the loop.
			self.screen.fill(self.settings.bg_color)
			self.ship.blitme()

			# Make the most recently drawn screen visible.
			pygame.display.flip()

	def _check_events(self):
		"""Respond toe keypresses and mouse events."""
		for event in pygame.event.get():
			if event.type == pygame.QUIT:
				sys.exit()
			elif event.type == pygame.KEYDOWN:
				self._check_keydown_events(event)
			elif event.type == pygame.KEYUP:
				self._check_keyup_events(event)

	def _check_keydown_events(self, event):
		"""Resopnd to keypresses."""
		if event.key == pygame.K_RIGHT:
			self.ship.moving_right = True
		elif event.key == pygame.K_LEFT:
			self.ship.moving_left = True
		elif event.key == pygame.K_q:
			sys.exit()
		elif event.key == pygame.K_SPACE:
			self._fire_bullet()

	def _check_keyup_events(self, event):
		"""Respond to key releases."""
		if event.key == pygame.K_RIGHT:
			self.ship.moving_right = False
		elif event.key == pygame.K_LEFT:
			self.ship.moving_left = False

	def _fire_bullet(self):
		"""Create a new bullet and add it to the bullets group."""
		if len(self.bullets) < self.settings.bullets_allowed:
			new_bullet = Bullet(self)
			self.bullets.add(new_bullet)

	def _update_bullets(self):
		"""Update position of bullets and get rid of old bullets."""
		# Update bullet positions.
		self.bullets.update()

		# Get rid fo bullets that have disappeared.
		for bullet in self.bullets.copy():
			if bullet.rect.bottom < 0:
				self.bullets.remove(bullet)

	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()
		for bullet in self.bullets.sprites():
			bullet.draw_bullet()

		pygame.display.flip()


if __name__ == '__main__':
	# Make a game instance, and run the game.
	ai = AlienInvasion()
	ai.run_game()