全局变量1
全局变量2
全局变量3
...
def 函数1():
  pass
def 函数2():
  pass
def 函数3():
  pass
def 函数4():
  pass
def 函数5():
  pass

class 类(object):
  属性1
  属性2
  def 方法1(self):
    pass
  def 方法2(self):
    pass
class 类2(object):
  属性3
  def 方法3(self):
    pass
  def 方法4(self):
    pass
  def 方法5(self):
    pass

class MiniOS(object):
  """MiniOS 操作系统类 """
  def __init__(self, name):
    self.name = name
    self.apps = [] # 安装的应用程序名称列表
  def __str__(self):
    return "%s 安装的软件列表为 %s" % (self.name, str(self.apps))
  def install_app(self, app):
    # 判断是否已经安装了软件
    if app.name in self.apps:
      print("已经安装了 %s，无需再次安装" % app.name)
    else:
      app.install()
      self.apps.append(app.name)
class App(object):
  def __init__(self, name, version, desc):
    self.name = name
    self.version = version
    self.desc = desc
  def __str__(self):
    return "%s 的当前版本是 %s - %s" % (self.name, self.version, self.desc)
  def install(self):
    print("将 %s [%s] 的执行程序复制到程序目录..." % (self.name, self.version))
class PyCharm(App):
  pass
class Chrome(App):
  def install(self):
    print("正在解压缩安装程序...")
    super().install()
linux = MiniOS("Linux")
print(linux)
pycharm = PyCharm("PyCharm", "1.0", "python 开发的 IDE 环境")
chrome = Chrome("Chrome", "2.0", "谷歌浏览器")
linux.install_app(pycharm)
linux.install_app(chrome)
linux.install_app(chrome)
print(linux)