On Mar 23, 8:01 pm, QS <[EMAIL PROTECTED]> wrote:
> Hi to all!
> I am new to python, and I encountered a weird problem.
>
> Here is my code
>
> ##########>8####################
> #!/usr/bin/python
> # Filename: objvar.py
> class Person:
> '''Represents a person.'''
>
> population = 0
> #sex = 'F'
> #age = 22
> # It is vague here: is this variable going to be a class, or
> object, variable
>
> def __init__(self, name, sex):
> '''Initializes the person's data.'''
> self.name = name
> self.sex = sex
> 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.'''
>
> self.age = 25
> print 'Hi, my name is %s, and I am %s, and I am age %d ' %
> (self.name, self.sex, self.age)
>
> 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', 'M')
> swaroop.sayHi()
> swaroop.howMany()
> kalam = Person('Abdul Kalam', 'M')
> kalam.sayHi()
> kalam.howMany()
> cathy = Person('Catherine', 'F')
> cathy.sayHi()
> cathy.howMany()
> swaroop.sayHi()
> swaroop.howMany()
>
> ############# 8< #########################
>
> When I run this script, I got the following exception:
> Exception exceptions.AttributeError: "'NoneType' object has no
> attribute 'population'" in <bound method Person.__del__ of
> <__main__.Person instance at 0xb7d8ac6c>> ignored
>
> To to newcomer like me, this message doesn't make much sense. What
> seems weird to me is that, if I change the variable cathy to something
> else, like cath, or even cat, then the script will finish gracefully.
> Why "cathy" is not liked?!!
>
> Some of you may have recognized that the code is derived from a sample
> code in Swaroop's "A byte of python".
>
> My python is of version 2.5.1, on Ubuntu.
That's really weird... it's reproducible on Windows too. It doesn't
make any sense why the name of the variable would make a difference.
My guess is you hit some kind of obscure bug.
George
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