Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #25571

Re: Encapsulation, inheritance and polymorphism

NNTP-Posting-Date Wed, 18 Jul 2012 09:40:02 -0500
Date Wed, 18 Jul 2012 15:40:00 +0100
From Lipska the Kat <lipska@lipskathekat.com>
User-Agent Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120410 Thunderbird/11.0.1
MIME-Version 1.0
Newsgroups comp.lang.python
Subject Re: Encapsulation, inheritance and polymorphism
References <x_udnUHnRNWDu5jNnZ2dnUVZ8tudnZ2d@bt.com> <3vnfd9-343.ln1@satorlaser.homedns.org> <-8SdnVrXGqie25jNnZ2dnUVZ7qKdnZ2d@bt.com> <roy-29E9DF.09525917072012@news.panix.com> <FNKdnU7rKqT46JjNnZ2dnUVZ8vGdnZ2d@bt.com> <ju4651$ivo$1@dough.gmane.org> <5005A103.9050802@stoneleaf.us> <mailman.2241.1342549103.4697.python-list@python.org> <Lb-dnVNwAtQOLZjNnZ2dnUVZ7r6dnZ2d@bt.com> <GHnNr.7895$Hs3.4746@fx08.am4> <5006b48a$0$29978$c3e8da3$5496439d@news.astraweb.com>
In-Reply-To <5006b48a$0$29978$c3e8da3$5496439d@news.astraweb.com>
Content-Type text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding 8bit
Message-ID <O4idnbBi5e1eV5vNnZ2dnUVZ8oydnZ2d@bt.com> (permalink)
Lines 87
X-Usenet-Provider http://www.giganews.com
X-AuthenticatedUsername NoAuthUser
X-Trace sv3-eOjremWHHSotZn327060sL4mPe8qE7Vjy4b00PrKF7/hWWGKmg/du9CFAKUVGe5cX6kLutBvnd1dJ8B!QF4o7PsDoTFR09URMQJYRz9FwHETESX5GGdmREHkpyJC8u9HFjR5uyWW+5jM/eBYd+/VgJgpNvY=
X-Complaints-To abuse@btinternet.com
X-DMCA-Complaints-To abuse@btinternet.com
X-Abuse-and-DMCA-Info Please be sure to forward a copy of ALL headers
X-Abuse-and-DMCA-Info Otherwise we will be unable to process your complaint properly
X-Postfilter 1.3.40
X-Original-Bytes 5449
Path csiph.com!usenet.pasdenom.info!news.stben.net!border3.nntp.ams.giganews.com!Xl.tags.giganews.com!border1.nntp.ams.giganews.com!nntp.giganews.com!local2.nntp.ams.giganews.com!nntp.bt.com!news.bt.com.POSTED!not-for-mail
Xref csiph.com comp.lang.python:25571

Show key headers only | View raw

On 18/07/12 14:05, Steven D'Aprano wrote:
> On Wed, 18 Jul 2012 01:46:31 +0100, Andrew Cooper wrote:
>
>> Take for example a Linux system call handler.  The general form looks a
>> little like (substituting C for python style pseudocode)
>>
>> if not (you are permitted to do this):
>>      return -EPERM
>> if not (you've given me some valid data):
>>      return -EFAULT
>> if not (you've given me some sensible data):
>>      return -EINVAL
>> return actually_try_to_do_something_with(data)
>>I’m feeling a bit fed uI’m feeling a bit fed uI’m feeling a bit fed u
>> How would you program this sort of logic with a single return statement?
>
> That's not terribly hard.
>
> if not (you are permitted to do this):
>      result = -EPERM
> elif not (you've given me some valid data):
>      result = -EFAULT
> elif not (you've given me some sensible data):
>      result = -EINVAL
> else:
>      result = actually_try_to_do_something_with(data)
> return result
>
>
> A better example would involve loops. I used to hate programming in some
> versions of Pascal without a break statement: I needed a guard variable
> to decide whether or not to do anything in the loop!
>
> # pseudo-code
> for i in 1 to 100:
>      if not condition:
>          do_something_useful()
>
>
> Even with a break, why bother continuing through the body of the function
> when you already have the result? When your calculation is done, it's
> done, just return for goodness sake. You wouldn't write a search that
> keeps going after you've found the value that you want, out of some
> misplaced sense that you have to look at every value. Why write code with
> unnecessary guard values and temporary variables out of a misplaced sense
> that functions must only have one exit?

Object Oriented programming is all about encapsulating human concepts in 
a way that makes sense to human beings. Make no mistake, it is NEVER the 
case that a software system is written for any other reason than to 
serve human beings. OO is more than just the mechanics of writing code, 
it's a state of mind.

OO was 'invented' to address the many problems that beset increasingly 
complex software systems. The main problem was maintainability. 
Encapsulating a concept in a clear and concise way makes the code easier 
to understand. Sometimes this means writing code that is not 'optimal' 
for the machine. Good code should be readable as well as efficient but I 
contend that it is better to write something that is clear, concise and 
well encapsulated than always go for the 'meanest dog in the scrapyard' 
approach where a developer is determined to write unreadable code that 
shows how jolly clever he is. More often than not he is forced to admit 
six months down the line that he has no idea what his code does as he 
'forgot' to comment it.

I speak from bitter experience. This approach works for me. I have 
thousands of lines of code operating every day 'in the wild', everything 
from flight booking systems to real time odds arbitrage. Any developer 
who 'gets' OO can read and modify my code and I am very proud of this 
fact ... and I have never been forced to admit that I don't know what I 
wrote six months ago.

If you are writing embedded systems that must have a very limited memory 
footprint then there is a case for conciseness over readability but even 
then it has to be maintainable

Python looks like an interesting language and I will certainly spend 
time getting to know it but at the moment it seems to me that calling it 
an Object Oriented language is just plain misleading.

There, I've said it, trolls and flamers beware, I take no prisoners.

Lipska

-- 
Lipska the Kat: Troll hunter, Sandbox destroyer
and Farscape dreamer of Aeryn Sun.

Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-17 09:45 +0100
  Re: Encapsulation, inheritance and polymorphism Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-07-17 06:03 -0400
    Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-17 12:24 +0100
      Re: Encapsulation, inheritance and polymorphism Larry Hudson <orgnut@yahoo.com> - 2012-07-18 00:10 -0700
  Re: Encapsulation, inheritance and polymorphism Ulrich Eckhardt <ulrich.eckhardt@dominolaser.com> - 2012-07-17 11:30 +0200
    Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-17 12:01 +0100
      Re: Encapsulation, inheritance and polymorphism Dave Angel <d@davea.name> - 2012-07-17 07:23 -0400
      Re: Encapsulation, inheritance and polymorphism Andrew Berg <bahamutzero8825@gmail.com> - 2012-07-17 06:37 -0500
        Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-17 12:44 +0100
          Re: Encapsulation, inheritance and polymorphism Andrew Berg <bahamutzero8825@gmail.com> - 2012-07-17 06:53 -0500
          Re: Encapsulation, inheritance and polymorphism Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-07-17 14:35 +0100
        Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-17 15:01 +0100
          Re: Encapsulation, inheritance and polymorphism Andrew Berg <bahamutzero8825@gmail.com> - 2012-07-17 09:16 -0500
            Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-17 15:26 +0100
          Re: Encapsulation, inheritance and polymorphism Terry Reedy <tjreedy@udel.edu> - 2012-07-17 13:30 -0400
          Re: Encapsulation, inheritance and polymorphism Andrew Berg <bahamutzero8825@gmail.com> - 2012-07-17 12:57 -0500
      Re: Encapsulation, inheritance and polymorphism Ulrich Eckhardt <ulrich.eckhardt@dominolaser.com> - 2012-07-17 14:18 +0200
      Re: Encapsulation, inheritance and polymorphism Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-07-17 14:29 +0100
      Re: Encapsulation, inheritance and polymorphism Roy Smith <roy@panix.com> - 2012-07-17 09:52 -0400
        Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-17 15:23 +0100
          Re: Encapsulation, inheritance and polymorphism Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-07-17 17:26 +0100
            Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-17 17:46 +0100
          Re: Encapsulation, inheritance and polymorphism Terry Reedy <tjreedy@udel.edu> - 2012-07-17 13:07 -0400
            Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-17 20:29 +0100
              Re: Encapsulation, inheritance and polymorphism Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-07-17 20:39 +0100
                Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-17 20:52 +0100
                Re: Encapsulation, inheritance and polymorphism John Ladasky <john_ladasky@sbcglobal.net> - 2012-08-18 23:05 -0700
                Re: Encapsulation, inheritance and polymorphism John Ladasky <john_ladasky@sbcglobal.net> - 2012-08-18 23:05 -0700
              Re: Encapsulation, inheritance and polymorphism Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-07-17 18:57 -0400
          Re: Encapsulation, inheritance and polymorphism Ethan Furman <ethan@stoneleaf.us> - 2012-07-17 10:29 -0700
          Re: Encapsulation, inheritance and polymorphism Chris Angelico <rosuav@gmail.com> - 2012-07-18 04:01 +1000
          Re: Encapsulation, inheritance and polymorphism Tim Chase <python.list@tim.thechases.com> - 2012-07-17 12:51 -0500
          Re: Encapsulation, inheritance and polymorphism Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-07-17 19:18 +0100
            Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-17 19:36 +0100
              Re: Encapsulation, inheritance and polymorphism Andrew Cooper <amc96@cam.ac.uk> - 2012-07-18 01:46 +0100
                Re: Encapsulation, inheritance and polymorphism rusi <rustompmody@gmail.com> - 2012-07-17 20:54 -0700
                Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-18 10:06 +0100
                Re: Encapsulation, inheritance and polymorphism Ulrich Eckhardt <ulrich.eckhardt@dominolaser.com> - 2012-07-18 14:01 +0200
                Re: Encapsulation, inheritance and polymorphism "BartC" <bc@freeuk.com> - 2012-07-19 01:41 +0100
                Re: Encapsulation, inheritance and polymorphism Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-18 13:05 +0000
                Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-18 15:40 +0100
                Re: Encapsulation, inheritance and polymorphism Chris Angelico <rosuav@gmail.com> - 2012-07-19 01:04 +1000
                Re: Encapsulation, inheritance and polymorphism Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-19 01:22 +0000
                Re: Encapsulation, inheritance and polymorphism Chris Angelico <rosuav@gmail.com> - 2012-07-19 15:09 +1000
                Re: Encapsulation, inheritance and polymorphism Ethan Furman <ethan@stoneleaf.us> - 2012-07-18 08:32 -0700
                Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-18 16:49 +0100
                Re: Encapsulation, inheritance and polymorphism Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-19 01:34 +0000
                Re: Encapsulation, inheritance and polymorphism rusi <rustompmody@gmail.com> - 2012-07-18 23:09 -0700
                Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-19 09:56 +0100
                Re: Encapsulation, inheritance and polymorphism rusi <rustompmody@gmail.com> - 2012-07-19 08:58 -0700
                Re: Encapsulation, inheritance and polymorphism Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-19 12:59 +0000
                Re: Encapsulation, inheritance and polymorphism Roy Smith <roy@panix.com> - 2012-07-19 09:06 -0400
                Re: Encapsulation, inheritance and polymorphism Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-20 07:24 +0000
                Re: Encapsulation, inheritance and polymorphism rusi <rustompmody@gmail.com> - 2012-07-20 01:21 -0700
                Re: Encapsulation, inheritance and polymorphism Paul Rudin <paul.nospam@rudin.co.uk> - 2012-07-19 18:22 +0100
                Re: Encapsulation, inheritance and polymorphism Tim Chase <python.list@tim.thechases.com> - 2012-07-19 13:20 -0500
                Re: Encapsulation, inheritance and polymorphism Chris Angelico <rosuav@gmail.com> - 2012-07-20 04:28 +1000
                Re: Encapsulation, inheritance and polymorphism Tim Chase <python.list@tim.thechases.com> - 2012-07-19 13:50 -0500
                Re: Encapsulation, inheritance and polymorphism Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-20 08:11 +0000
                Re: Encapsulation, inheritance and polymorphism Erik Max Francis <max@alcyone.com> - 2012-07-20 02:08 -0700
                Re: Encapsulation, inheritance and polymorphism "BartC" <bc@freeuk.com> - 2012-07-20 11:28 +0100
                Re: Encapsulation, inheritance and polymorphism Erik Max Francis <max@alcyone.com> - 2012-07-21 14:32 -0700
                Re: Encapsulation, inheritance and polymorphism Albert van der Horst <albert@spenarnc.xs4all.nl> - 2012-07-23 16:36 +0000
                Re: Encapsulation, inheritance and polymorphism Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-07-19 16:47 -0400
                Re: Encapsulation, inheritance and polymorphism John Gordon <gordon@panix.com> - 2012-07-19 21:01 +0000
                Re: Encapsulation, inheritance and polymorphism Chris Angelico <rosuav@gmail.com> - 2012-07-20 08:20 +1000
                Re: Encapsulation, inheritance and polymorphism John Gordon <gordon@panix.com> - 2012-07-19 22:23 +0000
                Re: Encapsulation, inheritance and polymorphism Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-20 08:27 +0000
                Re: Encapsulation, inheritance and polymorphism Virgil Stokes <vs@it.uu.se> - 2012-07-20 11:05 +0200
                Re: Encapsulation, inheritance and polymorphism Hans Mulder <hansmu@xs4all.nl> - 2012-07-20 19:45 +0200
                Re: Encapsulation, inheritance and polymorphism Erik Max Francis <max@alcyone.com> - 2012-07-21 14:28 -0700
                Re: Encapsulation, inheritance and polymorphism Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-07-20 13:57 -0400
                Re: Encapsulation, inheritance and polymorphism Ian Kelly <ian.g.kelly@gmail.com> - 2012-07-19 15:13 -0600
                Re: Encapsulation, inheritance and polymorphism Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-07-19 17:30 -0400
                Re: Encapsulation, inheritance and polymorphism Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-07-20 10:00 +0100
                Re: Encapsulation, inheritance and polymorphism Terry Reedy <tjreedy@udel.edu> - 2012-07-19 02:11 -0400
                Re: Encapsulation, inheritance and polymorphism Albert van der Horst <albert@spenarnc.xs4all.nl> - 2012-07-23 16:18 +0000
                Re: Encapsulation, inheritance and polymorphism Chris Angelico <rosuav@gmail.com> - 2012-07-24 02:15 +1000
                Re: Encapsulation, inheritance and polymorphism Robert Miles <robertmiles@teranews.com> - 2012-08-19 00:21 -0500
                Re: Encapsulation, inheritance and polymorphism Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-19 09:55 +0100
                Re: Encapsulation, inheritance and polymorphism lipska the kat <lipskathekat@yahoo.co.uk> - 2012-08-19 12:50 +0100
                Re: Encapsulation, inheritance and polymorphism Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-19 13:06 +0100
          Re: Encapsulation, inheritance and polymorphism Ethan Furman <ethan@stoneleaf.us> - 2012-07-17 11:43 -0700
          Re: Encapsulation, inheritance and polymorphism Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-07-17 15:05 -0400
          Re: Encapsulation, inheritance and polymorphism Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-07-17 20:33 +0100
          Re: Encapsulation, inheritance and polymorphism Ian <hobson42@gmail.com> - 2012-07-17 19:59 +0100
        Re: Encapsulation, inheritance and polymorphism Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-18 12:58 +0000
          Re: Encapsulation, inheritance and polymorphism Roy Smith <roy@panix.com> - 2012-07-18 09:07 -0400
            Re: Encapsulation, inheritance and polymorphism Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-18 14:31 +0000
          Re: Encapsulation, inheritance and polymorphism Dave Angel <d@davea.name> - 2012-07-18 12:33 -0400
            Re: Encapsulation, inheritance and polymorphism Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-19 01:23 +0000
      Re: Encapsulation, inheritance and polymorphism Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-18 12:43 +0000
      Re: Encapsulation, inheritance and polymorphism Grant Edwards <invalid@invalid.invalid> - 2012-07-18 14:34 +0000
        Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-18 15:48 +0100
          Re: Encapsulation, inheritance and polymorphism Chris Angelico <rosuav@gmail.com> - 2012-07-19 01:09 +1000
            Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-18 16:36 +0100
          Re: Encapsulation, inheritance and polymorphism Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-19 01:14 +0000
            Re: Encapsulation, inheritance and polymorphism MRAB <python@mrabarnett.plus.com> - 2012-07-19 02:28 +0100
              Re: Encapsulation, inheritance and polymorphism "OKB (not okblacke)" <brenNOSPAMbarn@NObrenSPAMbarn.net> - 2012-07-19 16:52 +0000
        Re: Encapsulation, inheritance and polymorphism Andrew Berg <bahamutzero8825@gmail.com> - 2012-07-18 10:00 -0500
  Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-17 13:01 +0100
    Re: Encapsulation, inheritance and polymorphism Terry Reedy <tjreedy@udel.edu> - 2012-07-17 13:24 -0400
      Re: Encapsulation, inheritance and polymorphism Lipska the Kat <lipska@lipskathekat.com> - 2012-07-17 19:21 +0100
    Re: Encapsulation, inheritance and polymorphism MRAB <python@mrabarnett.plus.com> - 2012-07-17 18:43 +0100
    Re: Encapsulation, inheritance and polymorphism Tim Chase <python.list@tim.thechases.com> - 2012-07-17 12:56 -0500
    Re: Encapsulation, inheritance and polymorphism Arnaud Delobelle <arnodel@gmail.com> - 2012-07-18 11:35 +0100

csiph-web