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Groups > comp.lang.python > #48980
| Date | 2013-06-23 22:35 +0900 |
|---|---|
| From | Adam Jiang <jiang.adam@gmail.com> |
| Subject | Re: What is the semantics meaning of 'object'? |
| References | <15ba0011-bbf1-42f7-b3ea-1c1d4b70e56b@googlegroups.com> <51c66962$0$29999$c3e8da3$5496439d@news.astraweb.com> |
| Newsgroups | comp.lang.python |
| Message-ID | <mailman.3726.1371994559.3114.python-list@python.org> (permalink) |
> * property only works in "new-style" classes that inherit from object;
>
> * likewise for super;
Another question raised here is that what is the proper way to refer
to parent class? For example,
class A(object):
def __init__(self, arg):
print "A"
class B(A):
def __init__(self, arg):
super(B, self).__init__(arg)
Is this correct? As the result, whenever you wanted to refer to a
method in parent class, super() functions has to be called. This seems
inefficient.
How to refer to a field defined in parent class?
Thanks,
/Adam
>On Sun, Jun 23, 2013 at 03:20:02AM +0000, Steven D'Aprano wrote:
> On Sat, 22 Jun 2013 19:58:38 -0700, Adam wrote:
>
> > class FooBar(object):
> > def __init__(self):
> > ...
> >
> > Inheritance usually takes a class name to indicate which class is the
> > 'parent' class. However, in the previous example, from a django book,
> > the class actually takes an 'object' like parameter, doesn't it? What is
> > the semantics meaning of such kind of notation?
>
> It's not merely notation, "object" is the name of a class. If you type it
> (without quotes) at the interactive interpreter, you will see it is a
> built-in class:
>
> py> object
> <class 'object'>
>
>
> In Python 3, the use of object as base class is optional, but in Python 2
> there is a subtle difference between classes that inherit from object and
> those that don't. The reason for this difference is buried in the mists
> of time, going back to Python 2.2. If you are interested, google on
> "Python unifying types and classes":
>
> https://duckduckgo.com/html/?q=Python+unifying+types+and+classes
>
>
> As a general rule, unless you actually want "old-style class" behaviour,
> you should always inherit from object (or some other built-in type) in
> Python 2. In Python 3, it doesn't matter.
>
> The differences include:
>
> * property only works in "new-style" classes that inherit from object;
>
> * likewise for super;
>
> * multiple inheritance with old-style classes can be buggy;
>
> * new-style classes may be slightly faster in general;
>
> * on the down side, automatic delegation of special double-underscore
> methods like __getitem__ and __str__ doesn't work with new-style classes.
>
>
> If none of this means anything to you, be glad, and just inherit from
> object or some other built-in type in all your classes, and all will be
> good.
>
>
>
>
> --
> Steven
> --
> http://mail.python.org/mailman/listinfo/python-list
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What is the semantics meaning of 'object'? Adam <jiang.adam@gmail.com> - 2013-06-22 19:58 -0700
Re: What is the semantics meaning of 'object'? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-23 03:20 +0000
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-22 22:27 -0600
Re: What is the semantics meaning of 'object'? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-23 05:23 +0000
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-22 23:40 -0600
Re: What is the semantics meaning of 'object'? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-23 17:29 +0000
Re: What is the semantics meaning of 'object'? Rotwang <sg552@hotmail.co.uk> - 2013-06-24 02:53 +0100
Re: What is the semantics meaning of 'object'? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-24 06:31 +0000
Re: What is the semantics meaning of 'object'? Rotwang <sg552@hotmail.co.uk> - 2013-06-24 16:00 +0100
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-24 11:23 -0600
Re: What is the semantics meaning of 'object'? Adam Jiang <jiang.adam@gmail.com> - 2013-06-23 22:35 +0900
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-23 10:15 -0600
Re: What is the semantics meaning of 'object'? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-23 16:35 +0000
Re: What is the semantics meaning of 'object'? Roy Smith <roy@panix.com> - 2013-06-23 12:49 -0400
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-23 11:08 -0600
Re: What is the semantics meaning of 'object'? Roy Smith <roy@panix.com> - 2013-06-23 14:14 -0400
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-23 11:18 -0600
Re: What is the semantics meaning of 'object'? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-23 17:36 +0000
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-23 12:04 -0600
Re: What is the semantics meaning of 'object'? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-23 18:50 +0000
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-23 13:09 -0600
Re: What is the semantics meaning of 'object'? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-24 01:12 +0000
Re: What is the semantics meaning of 'object'? Roy Smith <roy@panix.com> - 2013-06-23 15:24 -0400
Re: What is the semantics meaning of 'object'? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-24 01:27 +0000
Re: What is the semantics meaning of 'object'? Roy Smith <roy@panix.com> - 2013-06-23 21:38 -0400
Re: What is the semantics meaning of 'object'? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-24 08:06 +0000
Re: What is the semantics meaning of 'object'? Roy Smith <roy@panix.com> - 2013-06-24 08:41 -0400
Re: What is the semantics meaning of 'object'? Mark Janssen <dreamingforward@gmail.com> - 2013-06-24 08:58 -0700
Re: What is the semantics meaning of 'object'? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-24 23:51 +0000
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-24 11:26 -0600
Re: What is the semantics meaning of 'object'? Ethan Furman <ethan@stoneleaf.us> - 2013-06-26 13:14 -0700
Re: What is the semantics meaning of 'object'? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-26 23:54 +0000
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-26 19:03 -0600
Re: What is the semantics meaning of 'object'? Ethan Furman <ethan@stoneleaf.us> - 2013-06-26 17:38 -0700
Re: What is the semantics meaning of 'object'? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-23 18:46 +0000
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-23 13:05 -0600
Re: What is the semantics meaning of 'object'? Ethan Furman <ethan@stoneleaf.us> - 2013-06-26 13:37 -0700
Re: What is the semantics meaning of 'object'? Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-23 13:33 -0700
Re: What is the semantics meaning of 'object'? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-06-23 21:33 +0200
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-25 11:44 -0600
Re: What is the semantics meaning of 'object'? Mark Janssen <dreamingforward@gmail.com> - 2013-06-25 14:58 -0700
Re: What is the semantics meaning of 'object'? Chris Angelico <rosuav@gmail.com> - 2013-06-26 08:17 +1000
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-25 16:21 -0600
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-25 16:25 -0600
Re: What is the semantics meaning of 'object'? Mark Janssen <dreamingforward@gmail.com> - 2013-06-25 15:29 -0700
Re: What is the semantics meaning of 'object'? Mark Janssen <dreamingforward@gmail.com> - 2013-06-25 15:27 -0700
Re: What is the semantics meaning of 'object'? Mark Janssen <dreamingforward@gmail.com> - 2013-06-25 15:38 -0700
Re: What is the semantics meaning of 'object'? Chris Angelico <rosuav@gmail.com> - 2013-06-26 08:39 +1000
Re: What is the semantics meaning of 'object'? Chris Angelico <rosuav@gmail.com> - 2013-06-26 08:47 +1000
Re: What is the semantics meaning of 'object'? Chris Angelico <rosuav@gmail.com> - 2013-06-26 08:57 +1000
Re: What is the semantics meaning of 'object'? Rotwang <sg552@hotmail.co.uk> - 2013-06-26 16:16 +0100
Re: What is the semantics meaning of 'object'? Chris Angelico <rosuav@gmail.com> - 2013-06-27 01:23 +1000
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-25 17:07 -0600
Re: What is the semantics meaning of 'object'? Chris Angelico <rosuav@gmail.com> - 2013-06-26 09:08 +1000
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-25 17:10 -0600
Re: What is the semantics meaning of 'object'? Mark Janssen <dreamingforward@gmail.com> - 2013-06-25 16:19 -0700
Re: What is the semantics meaning of 'object'? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-26 08:36 +0000
Re: What is the semantics meaning of 'object'? alex23 <wuwei23@gmail.com> - 2013-06-28 10:19 +1000
Re: What is the semantics meaning of 'object'? Mark Janssen <dreamingforward@gmail.com> - 2013-06-28 11:55 -0700
Re: What is the semantics meaning of 'object'? Mark Janssen <dreamingforward@gmail.com> - 2013-06-25 16:00 -0700
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-25 18:19 -0600
Re: What is the semantics meaning of 'object'? Mark Janssen <dreamingforward@gmail.com> - 2013-06-25 18:07 -0700
Re: What is the semantics meaning of 'object'? Chris Angelico <rosuav@gmail.com> - 2013-06-26 17:25 +1000
Re: What is the semantics meaning of 'object'? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-26 02:53 -0600
Re: What is the semantics meaning of 'object'? Chris Angelico <rosuav@gmail.com> - 2013-06-26 09:54 +1000
Re: What is the semantics meaning of 'object'? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-06-26 12:56 +0200
Re: What is the semantics meaning of 'object'? Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-23 13:12 -0700
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