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Re: class object's attribute is also the instance's attribute?

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On 08/30/2012 06:55 AM, 陈伟 wrote:
> when i write code like this:
>
> class A(object):
>      
>     d = 'it is a doc.'
>     
>
> t = A()
>
> print t.__class__.d
> print t.d
>
> the output is same.
>
> so it means class object's attribute is also the instance's attribute. is it right? i can not understand it.

In your example, you have no instance attribute.  So when you use the
syntax to fetch one, the interpreter looks first at the instance,
doesn't find it, then looks in the class, and does.  That is documented
behavior.  Some people use it to provide a kind of default value for
instances, which can be useful if most instances need the same value,
but a few want to overrride it.

-- 

DaveA

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class object's attribute is also the instance's attribute? 陈伟 <chenwei.address@gmail.com> - 2012-08-30 03:55 -0700
  Re: class object's attribute is also the instance's attribute? Dave Angel <d@davea.name> - 2012-08-30 07:53 -0400
    Re: class object's attribute is also the instance's attribute? 陈伟 <chenwei.address@gmail.com> - 2012-08-30 05:57 -0700
    Re: class object's attribute is also the instance's attribute? 陈伟 <chenwei.address@gmail.com> - 2012-08-30 05:57 -0700
  Re: class object's attribute is also the instance's attribute? Ulrich Eckhardt <ulrich.eckhardt@dominolaser.com> - 2012-08-30 13:22 +0200
  Re: class object's attribute is also the instance's attribute? Marco Nawijn <nawijn@gmail.com> - 2012-08-30 05:34 -0700
    Re: class object's attribute is also the instance's attribute? Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-08-30 13:52 +0100
    Re: class object's attribute is also the instance's attribute? Hans Mulder <hansmu@xs4all.nl> - 2012-08-30 15:25 +0200
      Re: class object's attribute is also the instance's attribute? Marco Nawijn <nawijn@gmail.com> - 2012-08-30 07:11 -0700
        Re: class object's attribute is also the instance's attribute? Dave Angel <d@davea.name> - 2012-08-30 10:30 -0400
          Re: class object's attribute is also the instance's attribute? Marco Nawijn <nawijn@gmail.com> - 2012-08-30 07:48 -0700
            Re: class object's attribute is also the instance's attribute? Dave Angel <d@davea.name> - 2012-08-30 11:18 -0400
          Re: class object's attribute is also the instance's attribute? Marco Nawijn <nawijn@gmail.com> - 2012-08-30 07:48 -0700
            Re: class object's attribute is also the instance's attribute? Hans Mulder <hansmu@xs4all.nl> - 2012-08-30 17:20 +0200
              Re: class object's attribute is also the instance's attribute? Ben Finney <ben+python@benfinney.id.au> - 2012-08-31 09:58 +1000

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