Python论坛的帖子：

Mon Aug 29 18:14:06 HKT 2005

确实很奇怪，我把 __del__ 方法加了两行： 
   def __del__(self):
       '''I am dying.'''
       print '%s says bye.' % self.name;
       print '---'
       print dir(Person)

       Person.population -= 1;
       if Person.population == 0:
           print 'I am the last one.'
       else:
           print 'There are still %d people left.' % Person.population;

print dir(Person) 

结果，在 cmd 下独立运行，两次的结果完全不同

而在 idle 下，用 
del zhgx
del bazaari
的结果，就是正常的：

>>> 
(Initializing Bazaari)
Hello, my name is Bazaari
I am the only person here.
(Initializing zhgx)
Hello, my name is zhgx
We have 2 person here.
Hello, my name is Bazaari
zhgx says bye.
---
['HowMany', 'SayHi', '__del__', '__doc__', '__init__', '__module__',
'population']
There are still 1 people left.
Bazaari says bye.
---
['HowMany', 'SayHi', '__del__', '__doc__', '__init__', '__module__',
'population']
I am the last one.
>>> 


On 8/29/05, 广星 <guangxing at ict.ac.cn> wrote:
> 在学习Python，根据例子练习程序。
> 在类与对象的方法这一章中遇到了如下的问题，
> 困惑不已向大家请教。
> 
> 第一个问题：为什么在点击RUN的时候会报如下的提示呢？到底是不是错误》如果不是，到底是怎么回事呢？
> Exception exceptions.AttributeError: "'NoneType' object has no attribute 'population'" in <__main__.Person instance at 0x009335D0>> ignored
> 
> 第二个问题：脚本执行的结果如下，为什么会冒出来"zhgx says bye."呢？为什么在新生成对象的实例的时候自动调用了__del__呢？
> (Initializing Bazaari)
> Hello, my name is Bazaari
> I am the only person here.
> (Initializing zhgx)
> Hello, my name is zhgx
> We have 2 person here.
> Hello, my name is Bazaari
> zhgx says bye.
> There are still 1 people left.
> Bazaari says bye.
> 
> *************************************************************************************************************************
> ***************************************************源代码****************************************************************
> *************************************************************************************************************************
> #!/usr/bin/env python
> #Boa:PyApp:main
> 
> modules ={}
> 
> class Person:
>    '''Represents a person.'''
>    population = 0;
> 
>    def __init__(self, name):
>        '''Initializes the person's data.'''
>        self.name = name;
>        print '(Initializing %s)' % self.name
> 
>        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 'Hello, 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 person here.' % Person.population;
> 
> bazaari = Person('Bazaari');
> bazaari.SayHi();
> bazaari.HowMany();
> 
> zhgx = Person('zhgx');
> zhgx.SayHi();
> zhgx.HowMany();
> 
> bazaari.SayHi();
> *************************************************************************************************************************
> ***************************************************源代码****************************************************************
> *************************************************************************************************************************
> 
> 
> 广星
> guangxing at ict.ac.cn
> 2005-08-29
> 
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> python-chinese list
> python-chinese at lists.python.cn
> http://python.cn/mailman/listinfo/python-chinese
> 
> 
>

标题：Re: [python-chinese] 为啥会自动调用了__del__呢？

标题：Re: [python-chinese] 为啥会自动调用了del呢？