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Groups > comp.lang.python > #100279
| From | Robin Koch <robin.koch@t-online.de> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: Python variable assigning problems... |
| Date | 2015-12-11 18:52 +0100 |
| Organization | albasani.net |
| Message-ID | <n4f2hh$12u$1@news.albasani.net> (permalink) |
| References | <4b28ee3d-47b3-40ef-b48e-abff720635ed@googlegroups.com> <n4c0of$hqr$1@dont-email.me> <0098ce4a-966b-41df-bf06-352ad451134f@googlegroups.com> <n4etbt$mve$1@news.albasani.net> <mailman.144.1449852005.12405.python-list@python.org> |
Am 11.12.2015 um 17:39 schrieb Ian Kelly:
> On Fri, Dec 11, 2015 at 9:24 AM, Robin Koch <robin.koch@t-online.de> wrote:
>> Assigning goes from right to left:
>>
>> x,y=y,x=2,3
>>
>> <=>
>>
>> y, x = 2, 3
>> x, y = y, x
>>
>> Otherwise the assignment x, y = y, x would not make any sense, since x and y
>> haven't any values yet.
>>
>> And the execution from right to left is also a good choice, because one
>> would like to do something like:
>>
>> x = y = z = 0
>>
>> Again, assigning from left to right woud lead to errors.
>
> No, it actually happens left to right. "x = y = z = 0" means "assign 0
> to x, then assign 0 to y, then assign 0 to z." It doesn't mean "assign
> 0 to z, then assign z to y, etc."
Oh. Ok, then, thanks for this correction.
Although it's consequent to use left-to-right precedence it's a little
counter intuitive in the sense that the rightmost and leftmost objects
interact. Especially with a background in mathematics. :-)
> This works:
>
>>>> d = d['foo'] = {}
>>>> d
> {'foo': {...}}
>
> This doesn't:
>
>>>> del d
>>>> d['foo'] = d = {}
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> NameError: name 'd' is not defined
Good to know! Thank you.
--
Robin Koch
Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Python variable assigning problems... ICT Ezy <ictezy@gmail.com> - 2015-12-09 09:49 -0800
Re: Python variable assigning problems... Joel Goldstick <joel.goldstick@gmail.com> - 2015-12-09 12:51 -0500
Re: Python variable assigning problems... Joel Goldstick <joel.goldstick@gmail.com> - 2015-12-09 12:52 -0500
Re: Python variable assigning problems... Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-12-09 21:38 +0000
Re: Python variable assigning problems... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-12-10 16:33 +1100
Re: Python variable assigning problems... Denis McMahon <denismfmcmahon@gmail.com> - 2015-12-10 14:03 +0000
Re: Python variable assigning problems... ICT Ezy <ictezy@gmail.com> - 2015-12-11 08:10 -0800
Re: Python variable assigning problems... Robin Koch <robin.koch@t-online.de> - 2015-12-11 17:24 +0100
Re: Python variable assigning problems... Ian Kelly <ian.g.kelly@gmail.com> - 2015-12-11 09:39 -0700
Re: Python variable assigning problems... Robin Koch <robin.koch@t-online.de> - 2015-12-11 18:52 +0100
Re: Python variable assigning problems... ICT Ezy <ictezy@gmail.com> - 2015-12-11 10:23 -0800
Re: Python variable assigning problems... ICT Ezy <ictezy@gmail.com> - 2015-12-11 10:05 -0800
Re: Python variable assigning problems... Michael Torrie <torriem@gmail.com> - 2015-12-11 11:20 -0700
Re: Python variable assigning problems... ICT Ezy <ictezy@gmail.com> - 2015-12-11 10:25 -0800
Re: Python variable assigning problems... Jussi Piitulainen <harvesting@is.invalid> - 2015-12-11 20:27 +0200
Re: Python variable assigning problems... ICT Ezy <ictezy@gmail.com> - 2015-12-11 10:54 -0800
Re: Python variable assigning problems... ICT Ezy <ictezy@gmail.com> - 2015-12-11 10:55 -0800
Re: Python variable assigning problems... ICT Ezy <ictezy@gmail.com> - 2015-12-11 10:00 -0800
Re: Python variable assigning problems... Michael Torrie <torriem@gmail.com> - 2015-12-11 11:10 -0700
Re: Python variable assigning problems... Ian Kelly <ian.g.kelly@gmail.com> - 2015-12-11 09:36 -0700
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