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Groups > comp.lang.python > #71347
| From | Rotwang <sg552@hotmail.co.uk> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: Values and objects |
| Date | 2014-05-12 00:06 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <lkovpl$mgp$1@dont-email.me> (permalink) |
| References | (15 earlier) <536E799D.6080602@stoneleaf.us> <mailman.9869.1399764312.18130.python-list@python.org> <536eea59$0$29980$c3e8da3$5496439d@news.astraweb.com> <lknuv1$3ud$1@dont-email.me> <mailman.9892.1399833638.18130.python-list@python.org> |
On 11/05/2014 19:40, Ned Batchelder wrote:
> On 5/11/14 9:46 AM, Rotwang wrote:
>> On 11/05/2014 04:11, Steven D'Aprano wrote:
>>> [...]
>>>
>>> And try running
>>> this function in both 2.7 and 3.3 and see if you can explain the
>>> difference:
>>>
>>> def test():
>>> if False: x = None
>>> exec("x = 1")
>>> return x
>>
>> I must confess to being baffled by what happens in 3.3 with this
>> example. Neither locals() nor globals() has x = 1 immediately before the
>> return statement, so what is exec("x = 1") actually doing?
>>
>
> The same happens if you try to modify locals():
>
> >>> def test():
> ... if 0: x = 1
> ... locals()['x'] = 13
> ... return x
> ...
> >>> test()
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> File "<stdin>", line 4, in test
> UnboundLocalError: local variable 'x' referenced before assignment
>
> The doc for exec says:
>
> Note: The default locals act as described for function locals()
> below: modifications to the default locals dictionary should not be
> attempted. Pass an explicit locals dictionary if you need to see
> effects of the code on locals after function exec() returns.
>
> The doc for locals says:
>
> Note: The contents of this dictionary should not be modified;
> changes may not affect the values of local and free variables used
> by the interpreter.
>
> This is a tradeoff of practicality for purity: the interpreter runs
> faster if you don't make locals() a modifiable dict.
Thanks.
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Re: Pass variable by reference Ned Batchelder <ned@nedbatchelder.com> - 2014-05-06 16:31 -0400
Re: Pass variable by reference Mark H Harris <harrismh777@gmail.com> - 2014-05-06 16:00 -0500
Re: Pass variable by reference Ned Batchelder <ned@nedbatchelder.com> - 2014-05-06 17:27 -0400
Re: Pass variable by reference Chris Angelico <rosuav@gmail.com> - 2014-05-07 09:46 +1000
Re: Pass variable by reference Rustom Mody <rustompmody@gmail.com> - 2014-05-06 19:18 -0700
Re: Pass variable by reference Chris Angelico <rosuav@gmail.com> - 2014-05-07 12:39 +1000
Re: Pass variable by reference Rustom Mody <rustompmody@gmail.com> - 2014-05-06 19:54 -0700
Re: Pass variable by reference Steven D'Aprano <steve@pearwood.info> - 2014-05-07 04:59 +0000
Re: Pass variable by reference Mark H Harris <harrismh777@gmail.com> - 2014-05-07 13:11 -0500
Re: Pass variable by reference Marko Rauhamaa <marko@pacujo.net> - 2014-05-08 00:22 +0300
Values and objects [was Re: Pass variable by reference] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-08 01:08 +0000
Re: Values and objects [was Re: Pass variable by reference] Mark H Harris <harrismh777@gmail.com> - 2014-05-09 16:56 -0500
Re: Values and objects Marko Rauhamaa <marko@pacujo.net> - 2014-05-10 01:34 +0300
Re: Values and objects Ben Finney <ben@benfinney.id.au> - 2014-05-10 10:24 +1000
Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-10 01:01 +0000
Re: Values and objects Rustom Mody <rustompmody@gmail.com> - 2014-05-09 19:19 -0700
Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-10 12:33 +1000
Re: Values and objects Rustom Mody <rustompmody@gmail.com> - 2014-05-09 20:05 -0700
Re: Values and objects Mark H Harris <harrismh777@gmail.com> - 2014-05-09 23:15 -0500
Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-10 06:15 +0000
Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-10 17:21 +1000
Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-10 09:09 +0000
Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-10 19:32 +1000
Re: Values and objects Ethan Furman <ethan@stoneleaf.us> - 2014-05-10 12:10 -0700
Re: Values and objects MRAB <python@mrabarnett.plus.com> - 2014-05-10 20:22 +0100
Re: Values and objects Ethan Furman <ethan@stoneleaf.us> - 2014-05-10 12:28 -0700
Re: Values and objects Terry Reedy <tjreedy@udel.edu> - 2014-05-10 16:16 -0400
Re: Values and objects Terry Reedy <tjreedy@udel.edu> - 2014-05-10 16:24 -0400
Re: Values and objects Devin Jeanpierre <jeanpierreda@gmail.com> - 2014-05-10 14:03 -0700
Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 03:17 +0000
Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-11 13:30 +1000
Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 05:11 +0000
Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-11 15:22 +1000
Re: Values and objects Rustom Mody <rustompmody@gmail.com> - 2014-05-10 22:31 -0700
Re: Values and objects Marko Rauhamaa <marko@pacujo.net> - 2014-05-11 09:21 +0300
Re: Values and objects Rustom Mody <rustompmody@gmail.com> - 2014-05-10 23:48 -0700
Re: Values and objects Marko Rauhamaa <marko@pacujo.net> - 2014-05-11 18:10 +0300
Re: Values and objects Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-05-11 11:26 +0300
Re: Values and objects Rustom Mody <rustompmody@gmail.com> - 2014-05-11 01:48 -0700
Re: Values and objects Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-05-11 15:22 +0300
Re: Values and objects Marko Rauhamaa <marko@pacujo.net> - 2014-05-11 18:46 +0300
Re: Values and objects Marko Rauhamaa <marko@pacujo.net> - 2014-05-11 22:56 +0300
Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 12:51 +0000
Re: Values and objects Rustom Mody <rustompmody@gmail.com> - 2014-05-11 07:12 -0700
Re: Values and objects Ethan Furman <ethan@stoneleaf.us> - 2014-05-10 22:42 -0700
Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 06:40 +0000
Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-11 09:18 +1000
Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 03:11 +0000
Re: Values and objects Rotwang <sg552@hotmail.co.uk> - 2014-05-11 14:46 +0100
Re: Values and objects Ned Batchelder <ned@nedbatchelder.com> - 2014-05-11 14:40 -0400
Re: Values and objects Rotwang <sg552@hotmail.co.uk> - 2014-05-12 00:06 +0100
Re: Values and objects Ethan Furman <ethan@stoneleaf.us> - 2014-05-10 18:28 -0700
Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 07:24 +0000
Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-11 11:59 +1000
Re: Values and objects Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-11 07:29 +0000
Re: Values and objects Ethan Furman <ethan@stoneleaf.us> - 2014-05-10 21:46 -0700
Re: [Python-Dev] Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-11 16:08 +1000
Re: Values and objects albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-05-17 14:26 +0000
Re: Values and objects Chris Angelico <rosuav@gmail.com> - 2014-05-10 11:58 +1000
Re: Values and objects Marko Rauhamaa <marko@pacujo.net> - 2014-05-10 10:57 +0300
Re: Values and objects Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-05-10 11:06 +0300
Re: Values and objects Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-05-10 12:07 -0400
Re: Pass variable by reference Chris Angelico <rosuav@gmail.com> - 2014-05-08 11:31 +1000
Re: Pass variable by reference Mark H Harris <harrismh777@gmail.com> - 2014-05-09 17:30 -0500
Abstractions [was Re: Pass variable by reference] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-10 00:58 +0000
Re: Abstractions [was Re: Pass variable by reference] Mark H Harris <harrismh777@gmail.com> - 2014-05-09 21:17 -0500
Re: Pass variable by reference Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-07 01:14 +0000
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