Re: Python handles globals badly.

Path	csiph.com!news.mixmin.net!feeds.phibee-telecom.net!newsfeed.xs4all.nl!newsfeed8.news.xs4all.nl!news.tele.dk!news.tele.dk!small.news.tele.dk!newsgate.cistron.nl!newsgate.news.xs4all.nl!nzpost1.xs4all.net!not-for-mail
Return-Path	<rosuav@gmail.com>
X-Original-To	python-list@python.org
Delivered-To	python-list@mail.python.org
X-Spam-Status	OK 0.008
X-Spam-Evidence	'H': 0.98; 'S': 0.00; 'subject:Python': 0.05; 'assignment': 0.07; 'cc:addr:python-list': 0.09; 'dict': 0.09; 'sane': 0.09; 'def': 0.13; 'ah,': 0.16; 'cc:name:python': 0.16; 'empty),': 0.16; 'from:addr:rosuav': 0.16; 'from:name:chris angelico': 0.16; 'wrote:': 0.16; '(in': 0.18; '2015': 0.20; 'cc:2**0': 0.20; 'cc:addr:python.org': 0.20; 'logical': 0.22; 'sep': 0.22; 'am,': 0.23; 'sat,': 0.23; 'header:In-Reply-To:1': 0.24; 'sense': 0.26; 'updating': 0.27; 'message- id:@mail.gmail.com': 0.27; '[2]': 0.27; 'behaviour': 0.29; 'documenting': 0.29; 'starts': 0.29; 'certainly': 0.30; '[1]': 0.32; 'returned': 0.32; 'source': 0.33; 'received:google.com': 0.35; 'but': 0.36; 'created': 0.36; 'subject:: ': 0.37; '12,': 0.37; 'more': 0.63; '>>>>>': 0.66; 'worth': 0.67; 'chrisa': 0.84; 'locals': 0.84; 'thing...': 0.84; 'using.': 0.84; 'to:none': 0.91
DKIM-Signature	v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:cc :content-type; bh=9MODFJELWOr7Mqg1dTomAmYCakZe6DcdDafDMBD+OYo=; b=Fx8ZUtqNxG/iGvZJjJkfXhfLJbevGoaHiMIGRSpLzKMkcwnCKGBnzh6NC74R/RGOBb PKBrX2hNbWuPhDI0ldY8QXbJstbf74/dd2GTFwjV4Orku2I+ow8QExH9ylzptbMrqjV9 MLwuzPnLBluCunuwkjA0268MthXDfo7RVAj3xlKASoFUEXIEdFA8TxDqMj7ghUcEDUoD m01b8DEz9eKKwWp1KXqdrg0bd+9NGPXvlFaBJGg3ygCKp6uAxIaT/uBVu2eIOw11INwT WjT484Lwhra9EIb6XFnbTuJ0QY3ninpwj3mpHnMb2gJq+UgyZhvNRJBr9eVNsfAs/xcj Y8kQ==
MIME-Version	1.0
X-Received	by 10.107.41.142 with SMTP id p136mr4739979iop.19.1441986928352; Fri, 11 Sep 2015 08:55:28 -0700 (PDT)
In-Reply-To	<CALwzidmV93KnjEqq7avaf=R8WbhTuKuQDKF1SkjkoxZXFOsxxg@mail.gmail.com>
References	<c3363$547e74fe$5419aafe$24179@news.ziggo.nl> <cd7b7ffa-a217-4b62-bad2-9095b33a2bb6@googlegroups.com> <mailman.344.1441931751.8327.python-list@python.org> <55f293da$0$1640$c3e8da3$5496439d@news.astraweb.com> <CALwzidnG6kQFd5nqpN87b9AdsAan81=_FR=sfC+o3N93K28DNA@mail.gmail.com> <CAPTjJmqV0A9tw_bbDC8Z2NyTJfXGZszbkQdKwb4dXRkd89+bJw@mail.gmail.com> <CALwzid=6B9HzF-PwcEsaYLBKAWeA8QtPLhN4EQrWw17pNoJyKw@mail.gmail.com> <CAPTjJmoCuVMCXpTKeX+PvDw6rA9oyGPpQTxJ2VptbvvVu3x5yw@mail.gmail.com> <CALwzidmV93KnjEqq7avaf=R8WbhTuKuQDKF1SkjkoxZXFOsxxg@mail.gmail.com>
Date	Sat, 12 Sep 2015 01:55:28 +1000
Subject	Re: Python handles globals badly.
From	Chris Angelico <rosuav@gmail.com>
Cc	Python <python-list@python.org>
Content-Type	text/plain; charset=UTF-8
X-BeenThere	python-list@python.org
X-Mailman-Version	2.1.20+
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>
Newsgroups	comp.lang.python
Message-ID	<mailman.375.1441986932.8327.python-list@python.org> (permalink)
Lines	26
NNTP-Posting-Host	2001:888:2000:d::a6
X-Trace	1441986932 news.xs4all.nl 23747 [2001:888:2000:d::a6]:43857
X-Complaints-To	abuse@xs4all.nl
Xref	csiph.com comp.lang.python:96352

Show key headers only | View raw

On Sat, Sep 12, 2015 at 1:49 AM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
>> And that's the thing... I think. It's using locals(), which starts out
>> as a copy of the function's locals (in this example, empty), but
>> without assignment affecting anything. Which is more than a little
>> weird:
>>
>>>>> def f():
>> ...     x = [1]
>> ...     exec("print(x); x[0] = 2; print(x); x = [3]; print(x)")
>> ...     print(x)
>> ...
>>>>> f()
>> [1]
>> [2]
>> [3]
>> [2]
>
> Ah, that makes sense. It's writing into the dict that is created and
> returned by locals(), but not actually updating the frame locals which
> are the source of truth.

Yeah... but it only makes sense to people who understand the
implementation. It's certainly not a logical and sane behaviour that
would be worth documenting and using.

ChrisA

Thread

Re: Python handles globals badly. tdev@freenet.de - 2015-09-10 15:25 -0700
  Re: Python handles globals badly. Emile van Sebille <emile@fenx.com> - 2015-09-10 15:40 -0700
  Re: Python handles globals badly. Ian Kelly <ian.g.kelly@gmail.com> - 2015-09-10 18:35 -0600
    Re: Python handles globals badly. Marko Rauhamaa <marko@pacujo.net> - 2015-09-11 07:34 +0300
      Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-11 14:59 +1000
        Re: Python handles globals badly. Marko Rauhamaa <marko@pacujo.net> - 2015-09-11 08:15 +0300
          Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-11 15:25 +1000
          Re: Python handles globals badly. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-12 03:43 +0100
      Re: Python handles globals badly. Ian Kelly <ian.g.kelly@gmail.com> - 2015-09-10 23:07 -0600
        Re: Python handles globals badly. Marko Rauhamaa <marko@pacujo.net> - 2015-09-11 08:27 +0300
      Re: Python handles globals badly. Rustom Mody <rustompmody@gmail.com> - 2015-09-11 00:39 -0700
    Re: Python handles globals badly. Steven D'Aprano <steve@pearwood.info> - 2015-09-11 18:42 +1000
      Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-11 19:16 +1000
      Re: Python handles globals badly. Ian Kelly <ian.g.kelly@gmail.com> - 2015-09-11 09:03 -0600
        Re: Python handles globals badly. Steven D'Aprano <steve@pearwood.info> - 2015-09-12 17:00 +1000
      Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-12 01:15 +1000
      Re: Python handles globals badly. Ian Kelly <ian.g.kelly@gmail.com> - 2015-09-11 09:27 -0600
      Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-12 01:44 +1000
      Re: Python handles globals badly. Ian Kelly <ian.g.kelly@gmail.com> - 2015-09-11 09:49 -0600
      Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-12 01:55 +1000
      Re: Python handles globals badly. random832@fastmail.us - 2015-09-11 11:57 -0400
        Re: Python handles globals badly. Rustom Mody <rustompmody@gmail.com> - 2015-09-11 09:08 -0700
      Re: Python handles globals badly. Chris Angelico <rosuav@gmail.com> - 2015-09-12 02:04 +1000
      Re: Python handles globals badly. Ian Kelly <ian.g.kelly@gmail.com> - 2015-09-11 10:27 -0600
      Re: Python handles globals badly. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-12 03:51 +0100
  Re: Python handles globals badly. MRAB <python@mrabarnett.plus.com> - 2015-09-11 02:17 +0100
  Re: Python handles globals badly. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-09-12 03:27 +0100

csiph-web