oop_objvar.py

class Robot:
	"""Represents a robot, with a name."""
	# A class variable, counting the number of robots
	population = 0

	def __init__(self, name):
		"""Initializes the data."""
		self.name = name
		print "(Initializing {})".format(self.name)
		# When this person is created, the robot
		# adds to the population
		Robot.population += 1

	def die(self):
		"""I am dying."""
		print "{} is being destroyed!".format(self.name)
		Robot.population -= 1
		if Robot.population == 0:
			print "{} was the last one.".format(self.name)
		else:
			print "There are still {:d} robots working.".format(Robot.population)

	
	def say_hi(self):
		"""Greeting by the robot.
		Yeah, they can do that."""
		print "Greetings, my masters call me {}.".format(self.name)

	@classmethod
	def how_many(cls):
		"""Prints the current population."""
		print "We have {:d} robots.".format(cls.population)


droid1 = Robot("R2-D2")
droid1.say_hi()
Robot.how_many()
droid2 = Robot("C-3PO")
droid2.say_hi()
Robot.how_many()
print "\nRobots can do some work here.\n"
print "Robots have finished their work. So let's destroy them."
droid1.die()
droid2.die()
Robot.how_many()