Path: csiph.com!news.swapon.de!fu-berlin.de!uni-berlin.de!not-for-mail
From: Mark Lawrence <breamoreboy@yahoo.co.uk>
Newsgroups: comp.lang.python
Subject: Re: The Cost of Dynamism (was Re: Pyhon 2.x or 3.x, which is faster?)
Date: Tue, 22 Mar 2016 07:44:17 +0000
Lines: 62
Message-ID: <mailman.483.1458632710.12893.python-list@python.org>
References: <56e44258$0$1598$c3e8da3$5496439d@news.astraweb.com> <mailman.46.1457819135.12893.python-list@python.org> <8737rvxs89.fsf@elektro.pacujo.net> <nc2a7s$6dv$1@dont-email.me> <mailman.48.1457831488.12893.python-list@python.org> <nc4ffn$f6s$1@dont-email.me> <56e7483d$0$1608$c3e8da3$5496439d@news.astraweb.com> <nc7kjr$jj8$1@dont-email.me> <ncnhp9$tt7$1@dont-email.me> <mailman.426.1458526919.12893.python-list@python.org> <ncopi1$vgc$1@dont-email.me> <ncpave$50d$1@dont-email.me> <mailman.471.1458602403.12893.python-list@python.org> <ncq4kl$7cs$1@dont-email.me> <56f0ebe5$0$1497$c3e8da3$5496439d@news.astraweb.com> <8737rj561a.fsf@elektro.pacujo.net>
Mime-Version: 1.0
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0
In-Reply-To: <8737rj561a.fsf@elektro.pacujo.net>
Precedence: list
Xref: csiph.com comp.lang.python:105449

On 22/03/2016 07:24, Marko Rauhamaa wrote:
> Steven D'Aprano <steve+comp.lang.python@pearwood.info>:
>
>> I applaud you writing different versions of code to try different
>> tactics, but you should start from "write the most natural Python code
>> you can" *before* you trying guessing what's fast and what's slow.
>
> I'm hard-pressed to imagine a situation where I would write *unnatural*
> Python code for performance gains. Choosing a good algorithm applies to
> Python programming as well, but convoluted optimization tricks, hardly.
>
>> On Tuesday 22 March 2016 11:49, BartC wrote:
>>> No, it passes only a reference to the entire string.
>>
>> In Python terms, that *is* "the entire string".
>>
>> The point is, under the hood of the interpreter, *everything* passes
>> along references. We rarely draw attention to this fact. Given:
>>
>> function(1.5, [])
>>
>> we say "pass the float 1.5 and an empty list to function", not "pass a
>> reference to the float 1.5 and a reference to an empty list to a
>> reference to the function", because that would get rather annoying
>> quickly.
>
> Hm. Annoying to repeat, sure, but I don't know how you could extricate
> pointers from Python's abstract data model (or Java's, or Lisp's).
> Prolog or a purely functional programming language could get away
> without pointers but not Python.

I don't recall seeing any reference to "pointers" above.  In fact, I 
don't ever recall seeing references to pointers in the Python docs. 
There's certainly nothing here 
https://docs.python.org/3/reference/datamodel.html

>
>> But that's the critical point: it is *behind the scenes*, an
>> implementation detail.
>
> I don't think there is any way to implement, think about or define
> Python without pointers.

I never think about pointers, I think about objects.  Heck, I wouldn't 
have a clue as to how you go about implementing Jython or IronPython in 
terms of pointers.  I don't even know what anybody could mean by that.

>
>> In Python code, you don't pass "a reference to" 1.5, you pass 1.5.
>> Likewise for all other objects. The abstraction is that you pass
>> objects around, not references to objects.
>
> The devil is in the mutables...

Whereby these mysterious "pointers" suddenly leap into action I take it?

-- 
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.

Mark Lawrence