???????????

??????????????????????????????????????????????????????????????????????????????????? ?? ???????????????Щ?????????Щ???????????????Ч??

??????????? ?? ????????????????????????????????????? ??? ??????????????

?????? ???????????ж??????????????á????????????????????????????????????????????????????????????????????????????

???????? ????????????/?????С?????????????????????????????????????????????????????????????У????????????????????????????????????????????????????????????

??????????????

??11.4 ??????????????

#!/usr/bin/python
# Filename: objvar.py

class Person:
    '''Represents a person.'''
    population = 0

    def __init__(self, name):
        '''Initializes the person's data.'''
        self.name = name
        print '(Initializing %s)' % self.name

        # When this person is created, he/she
        # adds to the population
        Person.population += 1

    def __del__(self):
        '''I am dying.'''
        print '%s says bye.' % self.name

        Person.population -= 1

        if Person.population == 0:
            print 'I am the last one.'
        else:
            print 'There are still %d people left.' % Person.population

    def sayHi(self):
        '''Greeting by the person.

        Really, that's all it does.'''
        print 'Hi, my name is %s.' % self.name

    def howMany(self):
        '''Prints the current population.'''
        if Person.population == 1:
            print 'I am the only person here.'
        else:
            print 'We have %d persons here.' % Person.population

swaroop = Person('Swaroop')
swaroop.sayHi()
swaroop.howMany()

kalam = Person('Abdul Kalam')
kalam.sayHi()
kalam.howMany()

swaroop.sayHi()
swaroop.howMany()

????????code/objvar.py??

???

$ python objvar.py
(Initializing Swaroop)
Hi, my name is Swaroop.
I am the only person here.
(Initializing Abdul Kalam)
Hi, my name is Abdul Kalam.
We have 2 persons here.
Hi, my name is Swaroop.
We have 2 persons here.
Abdul Kalam says bye.
There are still 1 people left.
Swaroop says bye.
I am the last one.

????ι???

?????????????????????????????????????????????????????population????Person??????????????????name????????????????self???????????????????

?????????__init__????????????????????Person???????????????У???????population????1????????????????????????????????????self.name?????????????????????????????????????????????

?????????????self???????ο????????????????????????? ????ο? ??

??????????У??????????docstring????????????????á??????????????????Person.__doc__??Person.sayHi.__doc__??????????????????????????

?????__init__????????????????????????__del__????????????????????á???????????????????????????????潫????????????á?????????????棬???????????Person.population??1??

???????????????__del__???????У??????????????????????? ????? ???С???????????????????У????????del???????????????????????????????????

??C++/Java/C#??????????
Python?????е??????????????????????? ?????? ?????е???????? ??Ч?? ??
??????????????????????????????? ???????? ????__privatevar??Python????????????????Ч??????????б?????
?????????????????????????????????????????????????????????????????????????????????????????????????/??????á????????????????????????Python????????????????????????
????????__del__?????? destructor ??????????