Re: A question about Python Classes

References	<2219ee53-e8aa-4ac4-839f-014c3d1b1914@a19g2000prj.googlegroups.com> <mailman.716.1303410257.9059.python-list@python.org> <ios100$b0e$2@dont-email.me>
From	Ian Kelly <ian.g.kelly@gmail.com>
Date	2011-04-22 13:40 -0600
Subject	Re: A question about Python Classes
Newsgroups	comp.lang.python
Message-ID	<mailman.762.1303501291.9059.python-list@python.org> (permalink)

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On Fri, Apr 22, 2011 at 7:49 AM, Kyle T. Jones
<onexpadREMOVE@evomeryahoodotyouknow.com> wrote:
>> You don't need to create an instance of BaseHandler.  You have the
>> class, Python knows you have the class -- Python will look there if the
>> subclasses lack an attribute.
>>
>> ~Ethan~
>>
>
> Really?  That's not at all how I thought it worked in Python
> (post-instantiation referencing of class and superclass code...)

Yes, it looks up the attribute in the superclass tree at the time that
it's referenced, not at the time it's instantiated or at the time the
class is created.  So:

>>> class Base(object):
...     x = 5
...
>>> class Test(Base):
...     pass
...
>>> t = Test()
>>> t.x
5
>>> Test.x = 42
>>> t.x
42
>>> Base.x = 7
>>> del Test.x
>>> t.x
7

Or were you talking about something else?

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Thread

A question about Python Classes chad <cdalten@gmail.com> - 2011-04-21 08:43 -0700
  Re: A question about Python Classes Jean-Michel Pichavant <jeanmichel@sequans.com> - 2011-04-21 18:30 +0200
    Re: A question about Python Classes chad <cdalten@gmail.com> - 2011-04-21 09:46 -0700
  Re: A question about Python Classes "Pascal J. Bourguignon" <pjb@informatimago.com> - 2011-04-21 19:12 +0200
    Re: A question about Python Classes MRAB <python@mrabarnett.plus.com> - 2011-04-21 19:00 +0100
      Re: A question about Python Classes Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-04-22 01:53 +0000
    Re: A question about Python Classes Jean-Michel Pichavant <jeanmichel@sequans.com> - 2011-04-22 11:47 +0200
  Re: A question about Python Classes Terry Reedy <tjreedy@udel.edu> - 2011-04-21 13:39 -0400
  Re: A question about Python Classes Ethan Furman <ethan@stoneleaf.us> - 2011-04-21 11:34 -0700
    Re: A question about Python Classes "Kyle T. Jones" <onexpadREMOVE@EVOMERyahoodotyouknow.com> - 2011-04-22 08:49 -0500
      Re: A question about Python Classes Ethan Furman <ethan@stoneleaf.us> - 2011-04-22 12:38 -0700
      Re: A question about Python Classes Ian Kelly <ian.g.kelly@gmail.com> - 2011-04-22 13:40 -0600

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