class Robot:

population = 0

def __init__(self, name):

self.name = name

print("Initialize {0}".format(self.name))

Robot.population += 1

def __del__(self):

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 {0:d} robots working.".format(Robot.population))

def sayHi(self):

'''Greeting by the robot.

Yeah, they can do that.'''

print('Greetings, my master call me {}.'.format(self.name))

def howMany():

'''Prints the current population.'''

print('We have {0:d} robots.'.format(Robot.population))

howMany = staticmethod(howMany)

droid1 = Robot('R2-D2')

droid1.sayHi()

Robot.howMany()

droid2 = Robot('c-3PO')

droid2.sayHi()

Robot.howMany()

print("Robots have finished their work.So let's destroy them.")

del droid1

del droid2

Robot.howMany()