Python设计模式之命令模式简单示例

class Switch:
 ''' The INVOKER class'''
 def __init__(self, flipUpCmd, flipDownCmd):
  self.__flipUpCommand = flipUpCmd
  self.__flipDownCommand = flipDownCmd
 def flipUp(self):
  self.__flipUpCommand.execute()
 def flipDown(self):
  self.__flipDownCommand.execute()
class Light:
 '''The RECEIVER Class'''
 def turnOn(self):
  print "The light is on"
 def turnOff(self):
  print "The light is off"
class Command:
 """The Command Abstrace class"""
 def __init__(self):
  pass
 def execute(self):
  pass
class FlipUpCommand(Command):
 '''The Command class for turning on the light'''
 def __init__(self, light):
  self.__light = light
 def execute(self):
  self.__light.turnOn()
class FileDownCommand(Command):
 '''The Command class for turning off the light'''
 def __init__(self, light):
  Command.__init__(self)
  self.__light = light
 def execute(self):
  self.__light.turnOff()
class LightSwitch:
 '''The Client Class'''
 def __init__(self):
  self.__lamp = Light()
  self.__switchUp = FlipUpCommand(self.__lamp)
  self.__switchDown = FileDownCommand(self.__lamp)
  self.__switch = Switch(self.__switchUp, self.__switchDown)
 def switch(self, cmd):
  cmd = cmd.strip().upper()
  try:
   if cmd == "ON":
    self.__switch.flipUp()
   elif cmd == "OFF":
    self.__switch.flipDown()
   else:
    print "Argument \"ON\" or \"OFF\" is required"
  except Exception,msg:
   print "Exception occured:%s" % msg
#Execute if the file is run as a script and not imported as a module
if __name__ == "__main__":
 lightSwitch = LightSwitch()
 print "Switch ON test"
 lightSwitch.switch("ON")
 print "Switch OFF test"
 lightSwitch.switch("OFF")
 print "Invalid Command test"
 lightSwitch.switch("****")