Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: Erik <python@lucidity.plus.com>
Newsgroups: comp.lang.python
Subject: Re: Need help understanding list structure
Date: Mon, 2 May 2016 22:48:33 +0100
Lines: 28
Message-ID: <mailman.329.1462225716.32212.python-list@python.org>
References: <d6b0c524-f020-4726-b91a-517b2e8024ea@googlegroups.com> <5727CB31.5060309@lucidity.plus.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit
X-Trace: news.uni-berlin.de x7WckbD7VMq31zP3ZW6QIQSvP47dN/oRBl2i4FYTzBmA==
Return-Path: <python@lucidity.plus.com>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.001
X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'method.': 0.05; 'method,': 0.07; 'objects,': 0.07; 'subject:help': 0.07; 'iterate': 0.09; 'pointers': 0.09; 'itself.': 0.11; 'from:addr:python': 0.16; 'invoked,': 0.16; 'iterating': 0.16; 'pointers.': 0.16; 'received:84.93': 0.16; 'received:84.93.230': 0.16; 'received:io': 0.16; 'received:psf.io': 0.16; 'should.': 0.16; 'textual': 0.16; 'wrote:': 0.16; 'memory': 0.17; 'string': 0.17; 'element': 0.18; 'to:2**1': 0.21; 'text,': 0.22; "python's": 0.23; 'represents': 0.23; 'header:In-Reply-To:1': 0.24; 'header:User-Agent:1': 0.26; 'subject:list': 0.26; 'to:no real name:2**1': 0.27; 'function': 0.28; 'actual': 0.28; 'prints': 0.29; 'subject:skip:u 10': 0.29; 'objects': 0.29; 'print': 0.30; 'classes': 0.30; 'implement': 0.32; 'says': 0.32; 'received:84': 0.32; 'class': 0.33; 'list': 0.34; 'text': 0.35; 'according': 0.36; 'list,': 0.36; 'instead': 0.36; 'to:addr:python-list': 0.36; 'subject:: ': 0.37; 'expect': 0.37; 'method': 0.37; 'someone': 0.38; 'why': 0.39; 'whatever': 0.39; 'received:192': 0.39; 'to:addr:python.org': 0.40; 'where': 0.40; 'hope': 0.61; 'address': 0.61; 'subject:Need': 0.61; 'email addr:gmail.com': 0.62; 'charset:windows-1252': 0.62; "class's": 0.84
X-CM-Score: 0.00
X-CNFS-Analysis: v=2.1 cv=Iat6Ijea c=1 sm=1 tr=0 a=d6bQx1Csmutac+MnUcj9pQ==:117 a=d6bQx1Csmutac+MnUcj9pQ==:17 a=L9H7d07YOLsA:10 a=9cW_t1CCXrUA:10 a=s5jvgZ67dGcA:10 a=N659UExz7-8A:10 a=pGLkceISAAAA:8 a=r1hPsYAYBzlKzWqk7GkA:9 a=gq2ilWT529ViV0Om:21 a=py93SxM2iaYqzZFm:21 a=pILNOxqGKmIA:10
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2
In-Reply-To: <d6b0c524-f020-4726-b91a-517b2e8024ea@googlegroups.com>
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <https://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive: <http://mail.python.org/pipermail/python-list/>
List-Post: <mailto:python-list@python.org>
List-Help: <mailto:python-list-request@python.org?subject=help>
List-Subscribe: <https://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
X-Mailman-Original-Message-ID: <5727CB31.5060309@lucidity.plus.com>
X-Mailman-Original-References: <d6b0c524-f020-4726-b91a-517b2e8024ea@googlegroups.com>
Xref: csiph.com comp.lang.python:108032

On 02/05/16 22:30, moa47401@gmail.com wrote:
> Can someone help me understand why or under what circumstances a list
> shows pointers instead of the text data?

When Python's "print" statement/function is invoked, it will print the 
textual representation of the object according to its class's __str__ or
__repr__ method. That is, the print function prints out whatever text
the class says it should.

For classes which don't implement a __str__ or __repr__ method, then
the text "<CLASS object at ADDRESS>" is used - where CLASS is the class
name and ADDRESS is the "memory pointer".

 > If I iterate over the list, I do get the actual text of each element
 > and am able to use it.
 >
 > Also, if I iterate over the list and place each element in a new list
 > using append, then each element in the new list is the text I expect
 > not memory pointers.

Look at the __iter__ method of the class of the object you are iterating 
over. I suspect that it returns string objects, not the objects that are 
in the list itself.

String objects have a __str__ or __repr__ method that represents them as 
the text, so that is what 'print' will output.

Hope that helps, E.