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Date: Sat, 31 Aug 2013 00:03:58 -0700
From: Gary Herron <gherron@digipen.edu>
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Subject: Re: Encapsulation unpythonic?
References: <8255dfbd-a2a1-4ab7-b900-ee19faa459f2@googlegroups.com> <8c7c4854-70e1-46e7-a3ff-a3206c4c5c27@googlegroups.com> <5221567b$0$6599$c3e8da3$5496439d@news.astraweb.com> <ecd32f98-6ba8-4b1e-91d3-e0fd6a8034c3@googlegroups.com>
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On 08/30/2013 11:07 PM, Fabrice Pombet wrote:
> ... long discussion elided ...
> well, look at that:
>
> a=(1,2)
> a=2+3 ->a is an object and I have changed its type and value from outside. As far as I am concerned this is one hell of an encapsulation violation... Could you do this -strictly speaking- in Java or C++?

Yes, in fact you can do that in C++ and java:

Obj1 a = ...some object...;
{ // new scope...
    Obj2 a = ...another object...;
}

On one line, the name 'a' is bound to one object, and later it is bound 
to another object.   Your Python code is similar, binding the name 'a' 
to object (1,2) on one line and the object 5 on the next line.  Granted, 
Python seems a little freer because, with it's dynamic typing,  one 
doesn't need to create a new scope to rebind a name, but all languages 
with variable names allow some control over binding/rebinding names.

But this has *nothing* at all to do with objects and encapsulation.

Please don't confuse:

    the binding of names to objects and

    the existence of objects and their encapsulated behavior

They are very different things.

-- 
Dr. Gary Herron
Department of Computer Science
DigiPen Institute of Technology
(425) 895-4418


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    <div class="moz-cite-prefix">On 08/30/2013 11:07 PM, Fabrice Pombet
      wrote:<br>
    </div>
    <blockquote
      cite="mid:ecd32f98-6ba8-4b1e-91d3-e0fd6a8034c3@googlegroups.com"
      type="cite">... long discussion elided ...<br>
      <pre wrap="">
well, look at that:

a=(1,2)
a=2+3 -&gt;a is an object and I have changed its type and value from outside. As far as I am concerned this is one hell of an encapsulation violation... Could you do this -strictly speaking- in Java or C++?
</pre>
    </blockquote>
    <br>
    Yes, in fact you can do that in C++ and java:<br>
    <br>
    Obj1 a = ...some object...;<br>
    { // new scope...<br>
    &nbsp;&nbsp; Obj2 a = ...another object...;<br>
    }<br>
    <br>
    On one line, the name 'a' is bound to one object, and later it is
    bound to another object.&nbsp;&nbsp; Your Python code is similar, binding the
    name 'a' to object (1,2) on one line and the object 5 on the next
    line.&nbsp; Granted, Python seems a little freer because, with it's
    dynamic typing,&nbsp; one doesn't need to create a new scope to rebind a
    name, but all languages with variable names allow some control over
    binding/rebinding names.<br>
    <br>
    But this has *nothing* at all to do with objects and encapsulation.<br>
    <br>
    Please don't confuse:<br>
    <blockquote>the binding of names to objects and<br>
      <br>
      the existence of objects and their encapsulated behavior<br>
    </blockquote>
    They are very different things.<br>
    <br>
    <pre class="moz-signature" cols="72">-- 
Dr. Gary Herron
Department of Computer Science
DigiPen Institute of Technology
(425) 895-4418
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