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Groups > comp.lang.python > #100296
| Newsgroups | comp.lang.python |
|---|---|
| Date | 2015-12-11 10:55 -0800 |
| References | (2 earlier) <0098ce4a-966b-41df-bf06-352ad451134f@googlegroups.com> <n4etbt$mve$1@news.albasani.net> <mailman.144.1449852005.12405.python-list@python.org> <b09aa197-1945-4df7-8de6-2f2aeb28aba6@googlegroups.com> <lf5oadwhmd5.fsf@ling.helsinki.fi> |
| Message-ID | <b115fb40-2f78-4234-b3ff-98d813973f4c@googlegroups.com> (permalink) |
| Subject | Re: Python variable assigning problems... |
| From | ICT Ezy <ictezy@gmail.com> |
On Friday, December 11, 2015 at 10:27:29 AM UTC-8, Jussi Piitulainen wrote:
> ICT Ezy writes:
> > On Friday, December 11, 2015 at 8:40:18 AM UTC-8, Ian wrote:
> >>
> >> 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." 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
> >
> > Deat Ian,
> > Thank you very much your answer, but
> > above answer from Robin Koch and your answer is different. What's the
> > actually process here? I agree with Robin Koch, but your answer is
> > correct. Pl explain differences ?
>
> Python language reference, at 7.2 Assignment statements, says this:
>
> # An assignment statement evaluates the expression list (remember that
> # this can be a single expression or a comma-separated list, the latter
> # yielding a tuple) and assigns the single resulting object to each of
> # the target lists, from left to right.
>
> To simplify a bit, it's talking about a statement of this form:
>
> target_list = target_list = target_list = expression_list
>
> And it says what Ian said: the value of the expression is assigned to
> each target *from left to right*.
>
> <https://docs.python.org/3/reference/simple_stmts.html#assignment-statements>
See also:
>>> x = [5, 6]
>>> x[i],x[j]
(5, 6)
>>> i,j=0,1
>>> x[i],x[j]=x[j],x[i]=2,3
>>> x[i],x[j]
(3, 2)
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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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