Python论坛的帖子：

Mon Aug 29 20:12:49 HKT 2005

不奇怪,
由于GC的存在Python中__del__调用本来就在很多时候是不可预测的.
不过这个例子里面还是很明显的, 在
   zhgx = Person('zhgx');
   zhgx.SayHi();
   zhgx.HowMany();
后 zhgx 就没用了, 所以就自动清理掉了, 因此zhgx是在
bazaari前面del的.
这个顺序应该是在程序编译成字节码的时候就确定了.
Lee在IDEL里面是另一个情况, IDEL是解释器,
不当不能确定zhgx在以后是否会再用到,
所以zhgx不会自动del.

不知道解释清楚没~~,
我的建议是初学的时候不必太纠缠于这些细节.
python的好处就是不用自己做内存管理,
就用他的自动功能吧, 很舒服.

--- Albert Lee <hanzhupeng at gmail.com>写道:

> 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 > method Person.__del__ of <__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
> > 
> > _______________________________________________
> > python-chinese list
> > python-chinese at lists.python.cn
> > http://python.cn/mailman/listinfo/python-chinese
> > 
> > 
> >
> > _______________________________________________
> python-chinese list
> python-chinese at lists.python.cn
> http://python.cn/mailman/listinfo/python-chinese
> 

==========================================================

A student of Math in Soochow University in China.
Intrested in Math, Python, Octave, Lisp, Maxima, Prolog and .NET/MONO.

Blog: http://blog.sina.com.cn/blog/1142604745
Wiki: http://wiki.woodpecker.org.cn/moin/Hoxide

___________________________________________________________ 
雅虎免费G邮箱－No.1的防毒防垃圾超大邮箱 
http://cn.mail.yahoo.com

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？