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Date: Sun, 01 Sep 2013 21:15:03 -0700
From: Ethan Furman <ethan@stoneleaf.us>
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To: python-list@python.org
Subject: Re: Encapsulation unpythonic?
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On 09/01/2013 05:59 PM, Roy Smith wrote:
>   Ethan Furman wrote:
>> On 09/01/2013 02:54 PM, Tim Delaney wrote:
>>> Roy Smith wrote:
>>>>
>>>> Nothing is accessible in Python except via getters and setters.  The
>>>> only difference between Python and, say, C++ in this regard is that the
>>>> Python compiler writes them for you most of the time and doesn't make
>>>> you put ()'s at the end of the name
>>>
>>> I think Roy is referring to the fact that attribute access is implemented
>>> via __getattr__ / __getattribute__ /
>>> __setattr__ / __delattr__. From one point of view, he's absolutely correct
>>> - nearly all attributes are accessed via
>>> getters/setters in Python.
>>
>> Seems to me there is a difference between an underlying generic protocol for
>> data manipulation and "Python writing them
>> [getters/setters] for you".
>
> Why?  When I write "foo.bar", a bunch of generic code gets run which
> figures out what value to return.  If I don't like the generic behavior,
> I can write my own __getattrr__(), etc, and make it do whatever I want.

I don't yet know C++ so I can't speak to it.

In Python if you are writing your own __getattr__, etc., you are writing the underlying protocol itself.  To write a 
getter/setter you would just use

    def get_soemthing(...)
    def set_something(...)

or, even better

    @property
    def something(...)

Maybe, as Steven said, it's just a matter of degree:  my understanding of getters/setters is that they are per 
attribute, while __getattr__ will be called for every attribute not otherwise found, __setattr__ will be called for 
every assignment, __delattr__ will be called for every deletion, and all that is assuming you haven't written your own 
__getattribute__ and completely changed the rules for your class.

--
~Ethan~