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Re: Looking for a good introduction to object oriented programming with Python

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<8f1b60a5-0411-4aae-9ee6-0025b493ca2d@m13g2000vbd.googlegroups.com>,
 Jean Dubois <jeandubois314@gmail.com> wrote:

> Can someone here on this list give a trivial example of what object
> oriented programming is, using only Python?

OOP seems to mean different things to different people.  What OOP means 
to you is usually a strong function of whatever OOP language you learned 
first.  That being said, I think the fundamental, universal, core 
principle of OOP is that an object contains some data, and some code 
that knows how to do something with that data.

So, to give you a simple (but real-life) example, the system I'm working 
in now has User objects.  A user is a pretty complicated class, but 
here's some simple methods from it:

    def __eq__(self, other):
        return isinstance(other, (User, AnonymousUser)) \
          and self.user_id == other.user_id

    def __unicode__(self):
        return self.username

    def __repr__(self):
        return '<User %d: %r>' % (self.user_id, self.username)

This defines a few basic behaviors for User objects.

First, it defines how to tell if something is equal to a given User 
object.  The something must itself be a User (ignore the minor 
complication about AnonymousUser for the moment), and it must have the 
same user_id as this one.  I could easily imagine lots of other possible 
ways two users could be considered equal (same username, for example), 
but we're using user_id.  This means I can write:

   if user1 == user2:
      print "they're the same"

and I don't have to worry about (or even know about) the details.  In 
fact, sometime long after I've written that code, somebody could define 
some new kind of HighSecurityUser which tests for equality by comparing 
the scanned retina images for both of them.  My code wouldn't have to 
change; it would magically just start enforcing retina matching.

Likewise, I can write:

   print user

or

   logger.warning("%r did something interesting", user)

and I don't have to know anything about how to print a User.  The User 
knows how to print itself.

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[newbie] Looking for a good introduction to object oriented programming with Python Jean Dubois <jeandubois314@gmail.com> - 2012-08-04 08:49 -0700
  Re: [newbie] Looking for a good introduction to object oriented programming with Python shearichard@gmail.com - 2012-08-04 17:11 -0700
    Re: Looking for a good introduction to object oriented programming with Python Jean Dubois <jeandubois314@gmail.com> - 2012-08-05 05:38 -0700
    Re: Looking for a good introduction to object oriented programming with Python Jean Dubois <jeandubois314@gmail.com> - 2012-08-05 11:04 -0700
      Re: Looking for a good introduction to object oriented programming with Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-05 19:28 +0100
        Re: Looking for a good introduction to object oriented programming with Python Jean Dubois <jeandubois314@gmail.com> - 2012-08-06 07:56 -0700
          Re: Looking for a good introduction to object oriented programming with Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-06 17:17 +0100
            Re: Looking for a good introduction to object oriented programming with Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-07 01:12 +0000
              Re: Looking for a good introduction to object oriented programming with Python Ben Finney <ben+python@benfinney.id.au> - 2012-08-07 11:23 +1000
              Re: Looking for a good introduction to object oriented programming with Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-07 08:49 +0100
      Re: Looking for a good introduction to object oriented programming with Python Roy Smith <roy@panix.com> - 2012-08-05 14:39 -0400
      Re: Looking for a good introduction to object oriented programming with Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-05 19:53 +0100
      Re: Looking for a good introduction to object oriented programming with Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-05 18:45 -0400
        Re: Looking for a good introduction to object oriented programming with Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-05 22:51 +0000
          Re: Looking for a good introduction to object oriented programming with Python Roy Smith <roy@panix.com> - 2012-08-05 19:12 -0400
            Re: Looking for a good introduction to object oriented programming with Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-06 00:30 +0100
            Re: Looking for a good introduction to object oriented programming with Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-06 00:27 +0000
              Re: Looking for a good introduction to object oriented programming with Python Dan Sommers <dan@tombstonezero.net> - 2012-08-05 17:50 -0700
              Re: Looking for a good introduction to object oriented programming with Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-06 08:48 +0100
              Re: Looking for a good introduction to object oriented programming with Python DJC <djc@news.invalid> - 2012-08-06 11:20 +0200
            Re: Looking for a good introduction to object oriented programming with Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-05 20:57 -0400
          Re: Looking for a good introduction to object oriented programming with Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-06 08:43 +0100
            Re: Looking for a good introduction to object oriented programming with Python Roy Smith <roy@panix.com> - 2012-08-06 09:16 -0400
        Re: Looking for a good introduction to object oriented programming with Python Wolfgang Strobl <news4@mystrobl.de> - 2012-08-06 08:18 +0200
  Re: [newbie] Looking for a good introduction to object oriented programming with Python dncarac@gmail.com - 2012-08-05 11:59 -0700
  Re: [newbie] Looking for a good introduction to object oriented programming with Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-05 20:46 +0100
    Re: [newbie] Looking for a good introduction to object oriented programming with Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-05 23:11 +0100
      Re: [newbie] Looking for a good introduction to object oriented programming with Python Roy Smith <roy@panix.com> - 2012-08-05 18:53 -0400
    Re: [newbie] Looking for a good introduction to object oriented programming with Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-06 00:22 +0000
      Re: [newbie] Looking for a good introduction to object oriented programming with Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-06 02:02 +0100
      Re: [newbie] Looking for a good introduction to object oriented programming with Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-05 21:14 -0400
        Re: [newbie] Looking for a good introduction to object oriented programming with Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-06 06:08 +0000
          Re: [newbie] Looking for a good introduction to object oriented programming with Python Paul Rubin <no.email@nospam.invalid> - 2012-08-06 00:25 -0700
      Re: Looking for a good introduction to object oriented programming with Python alex23 <wuwei23@gmail.com> - 2012-08-05 19:44 -0700
        Re: Looking for a good introduction to object oriented programming with Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-07 19:02 +0000
          Re: Looking for a good introduction to object oriented programming with Python Terry Reedy <tjreedy@udel.edu> - 2012-08-07 18:37 -0400
          Re: Looking for a good introduction to object oriented programming with Python alex23 <wuwei23@gmail.com> - 2012-08-07 17:07 -0700
            Re: Looking for a good introduction to object oriented programming with Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-08 02:14 +0000
              Re: Looking for a good introduction to object oriented programming with Python Chris Angelico <rosuav@gmail.com> - 2012-08-08 12:24 +1000
              Re: Looking for a good introduction to object oriented programming with Python alex23 <wuwei23@gmail.com> - 2012-08-07 20:20 -0700
      Re: [newbie] Looking for a good introduction to object oriented programming with Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-06 09:55 +0100
        Re: [newbie] Looking for a good introduction to object oriented programming with Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-06 10:24 +0100
          Re: [newbie] Looking for a good introduction to object oriented programming with Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-07 05:35 +0000
            Re: [newbie] Looking for a good introduction to object oriented programming with Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-07 09:16 +0100
        Re: [newbie] Looking for a good introduction to object oriented programming with Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-07 05:19 +0000
          Re: [newbie] Looking for a good introduction to object oriented programming with Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-07 10:19 +0100
            Re: [newbie] Looking for a good introduction to object oriented programming with Python Ben Finney <ben+python@benfinney.id.au> - 2012-08-07 23:12 +1000
              Re: [newbie] Looking for a good introduction to object oriented programming with Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-07 15:13 +0100
            Re: [newbie] Looking for a good introduction to object oriented programming with Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-07 14:14 +0000
              Re: [newbie] Looking for a good introduction to object oriented programming with Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-07 15:34 +0100
                Re: Looking for a good introduction to object oriented programming with Python rusi <rustompmody@gmail.com> - 2012-08-07 08:04 -0700
                Re: Looking for a good introduction to object oriented programming with Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-07 18:00 +0100
                Re: Looking for a good introduction to object oriented programming with Python Chris Angelico <rosuav@gmail.com> - 2012-08-08 07:57 +1000
                Re: Looking for a good introduction to object oriented programming with Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-08 10:51 +0100
                Re: Looking for a good introduction to object oriented programming with Python rusi <rustompmody@gmail.com> - 2012-08-08 09:27 -0700
                Re: Looking for a good introduction to object oriented programming with Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-08 17:28 +0000
                Re: Looking for a good introduction to object oriented programming with Python Chris Angelico <rosuav@gmail.com> - 2012-08-09 11:32 +1000
                Re: Looking for a good introduction to object oriented programming with Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-08 12:42 -0400
                Re: Looking for a good introduction to object oriented programming with Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-08 20:31 +0100
                Re: Looking for a good introduction to object oriented programming with Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-08 22:59 -0400
                Re: Looking for a good introduction to object oriented programming with Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-09 08:29 +0100
                Geneology Packages -- WAS: Looking for a good introduction to object oriented programming with Python Simon Cropper <simoncropper@fossworkflowguides.com> - 2012-08-09 13:51 +1000
                Re: Geneology Packages Ben Finney <ben+python@benfinney.id.au> - 2012-08-09 14:00 +1000
    Re: Looking for a good introduction to object oriented programming with Python rusi <rustompmody@gmail.com> - 2012-08-06 05:19 -0700
      Re: Looking for a good introduction to object oriented programming with Python lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-06 15:27 +0100
        Re: Looking for a good introduction to object oriented programming with Python rusi <rustompmody@gmail.com> - 2012-08-06 09:34 -0700
          Re: Looking for a good introduction to object oriented programming with Python Chris Angelico <rosuav@gmail.com> - 2012-08-07 08:44 +1000
      OT probably but still relevant (was Re: Looking for a good introduction to object oriented programming with Python) lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-06 17:23 +0100
        Re: OT probably but still relevant (was Re: Looking for a good introduction to object oriented programming with Python) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-07 09:44 +0000
          Re: OT probably but still relevant (was Re: Looking for a good introduction to object oriented programming with Python) lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-07 11:23 +0100

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