同一根目录下不同的py文件，为什么不用导入却可以访问并修改其他py文件中类的属性值？
例如从入门到实践中的12.5章节game_function模块访问修改ship模块下的movin_right属性值：
game_function模块代码如下：
import sys
import pygame
from bullet import Bullet
#此处并未导入ship
def check_keydown_event(event,ai_settings,screen,ship,bullets):
"""相应按键事件"""
if event.key == pygame.K_RIGHT:
ship.moving_right = True
elif event.key == pygame.K_LEFT:
ship.moving_left = True
elif event.key == pygame.K_UP:
ship.moving_up = True
elif event.key == pygame.K_DOWN:
ship.moving_down = True
#修改了ship中的属性值
elif event.key == pygame.K_SPACE:
fire_bullet(ai_settings,screen,ship,bullets)
def check_keyup_event(event,ship):
"""相应松开事件"""
if event.key == pygame.K_RIGHT:
ship.moving_right = False
elif event.key == pygame.K_LEFT:
ship.moving_left = False
elif event.key == pygame.K_UP:
ship.moving_up = False
elif event.key == pygame.K_DOWN:
ship.moving_down = False
def check_events(ai_settings,screen,ship,bullets):
"""响应按键和鼠标事件"""
for event in pygame.event.get():
if event.type == pygame.QUIT:
sys.exit()
elif event.type == pygame.KEYDOWN:
check_keydown_event(event,ai_settings,screen,ship,bullets)
elif event.type == pygame.KEYUP:
check_keyup_event(event,ship)
def update_screen(ai_settings,screen,ship,bullets):
"""更新屏幕的图像并切换到新屏幕"""
#每次循环时都重新绘制屏幕
screen.fill(ai_settings.bg_color)
#在飞船和外星人后面重绘所有子弹
for bullet in bullets.sprites():
bullet.draw_bullet()
ship.blitme()
#让最近绘制的屏幕可见
pygame.display.flip()
def update_bullets(bullets):
"""更新子弹位置，并删除已消失的子弹"""
#更新子弹位置
bullets.update()
#删除已消失的子弹
for bullet in bullets.copy():
if bullet.rect.bottom <= 0:
bullets.remove(bullet)
def fire_bullet(ai_settings,screen,ship,bullets):
"""如果子弹还没达到上限，就发射一个子弹"""
if len(bullets) < ai_settings.bullets_allowed:
new_bullet = Bullet(ai_settings, screen, ship)
bullets.add(new_bullet)
ship模块代码如下：
import pygame
class Ship():
def __init__(self,ai_settings,screen):
"""初始化飞船并初始化其位置"""
self.screen = screen
#加载飞船图像并获取其外接矩形
self.image = pygame.image.load('images/ship.bmp')#加载图片
self.rect = self.image.get_rect()#图片赋予给显示矩形
self.screen_rect = screen.get_rect()#将显示矩形赋予给screen_rect
self.ai_settings = ai_settings#引用settings
#将每艘船放在屏幕底部中央
self.rect.centerx = self.screen_rect.centerx #飞船的中心x坐标 设置为表示屏幕的矩形属性cenrerx
self.rect.bottom = self.screen_rect.bottom #飞船的下边缘y坐标 设置为表示屏幕的矩形属性bottom
#centerx-中心线，bottom-底部
#在飞船的属性centen存储小数值
self.center = float(self.rect.centerx)
#移动标志
self.moving_right = False
self.moving_left = False
self.moving_up = False
self.moving_down = False
def update(self):
"""根据标志移动飞船位置"""
#更新飞船的centerx值而不是rect
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
if self.moving_up:
self.rect.top -= self.ai_settings.ship_speed_factor
if self.rect.top < 0:
self.rect.top = self.screen_rect.top
if self.moving_down:
self.rect.bottom += self.ai_settings.ship_speed_factor
if self.rect.bottom > 700:
self.rect.bottom = self.screen_rect.bottom
#根据self.centerx更新rect对象
self.rect.centerx = self.center
def blitme(self):
"""在指定位置绘制飞船"""
self.screen.blit(self.image,self.rect)
