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Re: Question about Pass-by-object-reference?

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From Ned Batchelder <ned@nedbatchelder.com>
Subject Re: Question about Pass-by-object-reference?
Date Tue, 22 Jul 2014 15:32:19 -0400
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On 7/22/14 3:04 PM, fl wrote:
> Hi,
> I learn Python function call on tutorial. There is a link on this subject.
> http://robertheaton.com/2014/02/09/pythons-pass-by-object-reference-as-explained-by-philip-k-dick/
>
> Although it explains clearly, the figure makes me puzzled.
>
> ""Python is different. As we know, in Python, "Object references are passed by
> value".
>
> A function receives a reference to (and will access) the same object in memory as
> used by the caller. However, it does not receive the box that the caller is
> storing this object in; as in pass-by-value, the function provides its own box and
> creates a new variable for itself. Let's try appending again:""
>
> On the figure, it shows that the result is [0, 1]  (Am I right on the figure?)
>

This is a topic that often confuses people new to Python.  The article 
you linked to seems very confusing to me.  My own take on how to explain 
it is here: http://nedbatchelder.com/text/names.html

>
> When I enter the command lines on my computer:
>>>> list=[0]
>>>> append(list)
>>>> print(list)
> [0]
>
> How to understand my result and that figure?

You should have gotten [0, 1], you must have different code than was 
shown in the article.  I recommend putting the code into a .py file, and 
running it all at once.  Then if it doesn't do what you expect, you can 
show the entire .py file when asking for help.

>
>
>
> Thanks,
>


-- 
Ned Batchelder, http://nedbatchelder.com

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Thread

Question about Pass-by-object-reference? fl <rxjwg98@gmail.com> - 2014-07-22 12:04 -0700
  Re: Question about Pass-by-object-reference? Ned Batchelder <ned@nedbatchelder.com> - 2014-07-22 15:32 -0400
    Re: Question about Pass-by-object-reference? fl <rxjwg98@gmail.com> - 2014-07-22 12:54 -0700
  Re: Question about Pass-by-object-reference? fl <rxjwg98@gmail.com> - 2014-07-22 12:34 -0700
    Re: Question about Pass-by-object-reference? Peter Pearson <ppearson@nowhere.invalid> - 2014-07-22 20:35 +0000
      Re: Question about Pass-by-object-reference? emile <emile@fenx.com> - 2014-07-22 13:46 -0700
        Re: Question about Pass-by-object-reference? fl <rxjwg98@gmail.com> - 2014-07-22 15:17 -0700
          Re: Question about Pass-by-object-reference? Joel Goldstick <joel.goldstick@gmail.com> - 2014-07-22 18:26 -0400
          Re: Question about Pass-by-object-reference? emile <emile@fenx.com> - 2014-07-22 15:33 -0700
          Re: Question about Pass-by-object-reference? Jerry Hill <malaclypse2@gmail.com> - 2014-07-22 19:06 -0400
        Re: Question about Pass-by-object-reference? fl <rxjwg98@gmail.com> - 2014-07-22 15:31 -0700
          Re: Question about Pass-by-object-reference? emile <emile@fenx.com> - 2014-07-22 15:40 -0700
      Re: Question about Pass-by-object-reference? fl <rxjwg98@gmail.com> - 2014-07-22 16:00 -0700
        Re: Question about Pass-by-object-reference? emile <emile@fenx.com> - 2014-07-22 16:10 -0700
  Re: Question about Pass-by-object-reference? Terry Reedy <tjreedy@udel.edu> - 2014-07-22 20:27 -0400
    Re: Question about Pass-by-object-reference? fl <rxjwg98@gmail.com> - 2014-07-22 18:49 -0700
      Re: Question about Pass-by-object-reference? Ben Finney <ben+python@benfinney.id.au> - 2014-07-23 11:59 +1000
        Re: Question about Pass-by-object-reference? Steven D'Aprano <steve@pearwood.info> - 2014-07-23 05:35 +0000
          Re: Question about Pass-by-object-reference? Chris Angelico <rosuav@gmail.com> - 2014-07-23 16:07 +1000
          Re: Question about Pass-by-object-reference? Ben Finney <ben+python@benfinney.id.au> - 2014-07-23 16:25 +1000
          Re: Question about Pass-by-object-reference? Terry Reedy <tjreedy@udel.edu> - 2014-07-23 18:51 -0400
            Re: Question about Pass-by-object-reference? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-07-24 03:22 +0000
              Re: Question about Pass-by-object-reference? Steven D'Aprano <steve@pearwood.info> - 2014-07-24 05:05 +0000
    Re: Question about Pass-by-object-reference? Steven D'Aprano <steve@pearwood.info> - 2014-07-23 05:36 +0000
      Re: Question about Pass-by-object-reference? Terry Reedy <tjreedy@udel.edu> - 2014-07-23 18:32 -0400
    Re: Question about Pass-by-object-reference? alex23 <wuwei23@gmail.com> - 2014-07-25 15:20 +1000
  Re: Question about Pass-by-object-reference? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-07-23 01:56 +0000

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