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Groups > comp.lang.python > #48695
| From | Νίκος <support@superhost.gr> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: A certainl part of an if() structure never gets executed. |
| Date | 2013-06-19 10:49 +0300 |
| Organization | GRNET - Greek Research and Technology Network |
| Message-ID | <kprnpm$2mj$1@news.grnet.gr> (permalink) |
| References | (8 earlier) <mailman.3277.1371201144.3114.python-list@python.org> <kpeorl$spl$7@news.ntua.gr> <ro5qr89r11ebtqif6hr9egkkr1s4ecogef@4ax.com> <kpjsfi$hmp$2@news.ntua.gr> <e2e2s8pbfbvequ26icu1avilqjcod48san@4ax.com> |
Στις 19/6/2013 8:08 πμ, ο/η Tim Roberts έγραψε:
> Nick the Gr33k <support@superhost.gr> wrote:
>>
>> On 16/6/2013 4:55 ??, Tim Roberts wrote:
>>
>>> Nick the Gr33k <support@superhost.gr> wrote:
>>> Because Python lets you use arbitrary values in a Boolean context, the net
>>> result is exactly the same.
>>
>> What is an arbitrary value? don even knwo what arbitrary means literally
>> in English.
>
> Basically, it means "any". In Python, you can use ANY value where a
> Boolean is expected. All types have a Boolean meaning. For integers, 0 is
> false, anything else is true. For strings, an empty string "" is false,
> anything else is true. For lists, an empty list [] is false, anything else
> is true. For tuples, an empty tuple () is false, anything else is true.
> For dicts, an empty dict {} is false, anything else is true.
>
>> The argument being returned in an "and" or "or" expression is the one
>> that *determined' the evaluation of the expression.
>
> That's not exactly how I'd put it, but the statement is correct. The last
> thing it had to evaulate is the result of the expression.
>
>> And actually what's being returned is not the argument itself but the
>> argument's value.
>
> But this is no different than any other programming language. Expressions
> always use the value of their operands, and they always return a value.
>
> The name vs value thing is critical to understanding Python, in my opinion,
> and it can be a stumbling block when you're coming from another language.
> Here's how I think about it.
>
> Python had two distinct spaces: there is a space for names, and there is a
> space for objects (which are values). Objects live in a nameless, faceless
> object cloud.
>
> A name is always bound to some object (which might be the "None" object). A
> name always knows its object, but an object never knows what names it is
> bound to.
>
> The only things that can be used in expressions and function arguments are
> objects. Names are merely the way we specify which objects to be used.
>
> a = [3]
>
> That creates a nameless list containing a single integer object with the
> value 3. It then binds the name "a" to that list. Note that the list has
> no clue that it is bound to any names.
>
> b = a
>
> That binds "b" to the same list. "b" and "a" are not related in any way,
> except that they happen to be bound to the same object. Note that there is
> still only one list.
>
> a.append(4)
>
> That modifies the list so that it now contains [3,4]. b is bound to the
> same list, so if you
> print(b)
> you'll see [3,4]
>
> Now, let's say I do this:
>
> a = [5]
>
> Here's where people get tripped up. This does not change our original
> list. Instead, it creates a new nameless list containing 5, and binds the
> name a to that list. a and b are no longer bound to the same object.
>
Thank you very much Tim for the simply and detailed put explanation.
--
What is now proved was at first only imagined!
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Re: A certainl part of an if() structure never gets executed. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-13 01:55 +0000
Re: A certainl part of an if() structure never gets executed. Chris Angelico <rosuav@gmail.com> - 2013-06-13 12:03 +1000
Re: A certainl part of an if() structure never gets executed. Kushal Kumaran <kushal.kumaran+python@gmail.com> - 2013-06-13 10:05 +0530
Re: A certainl part of an if() structure never gets executed. Chris Angelico <rosuav@gmail.com> - 2013-06-13 14:39 +1000
Re: A certainl part of an if() structure never gets executed. Νικόλαος Κούρας <support@superhost.gr> - 2013-06-13 08:36 +0300
Re: A certainl part of an if() structure never gets executed. Νικόλαος Κούρας <support@superhost.gr> - 2013-06-13 10:11 +0300
Re: A certainl part of an if() structure never gets executed. Sibylle Koczian <nulla.epistola@web.de> - 2013-06-13 14:22 +0200
Re: A certainl part of an if() structure never gets executed. Νικόλαος Κούρας <support@superhost.gr> - 2013-06-13 17:26 +0300
Re: A certainl part of an if() structure never gets executed. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-14 01:14 +0000
Re: A certainl part of an if() structure never gets executed. Nick the Gr33k <support@superhost.gr> - 2013-06-14 11:03 +0300
Re: A certainl part of an if() structure never gets executed. Chris Angelico <rosuav@gmail.com> - 2013-06-14 18:23 +1000
Re: A certainl part of an if() structure never gets executed. "R. Michael Weylandt" <michael.weylandt@gmail.com> - 2013-06-14 09:24 +0100
Re: A certainl part of an if() structure never gets executed. Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-06-14 11:28 +0300
Re: A certainl part of an if() structure never gets executed. Nick the Gr33k <support@superhost.gr> - 2013-06-14 11:41 +0300
Re: A certainl part of an if() structure never gets executed. Chris Angelico <rosuav@gmail.com> - 2013-06-14 18:50 +1000
Re: A certainl part of an if() structure never gets executed. Fábio Santos <fabiosantosart@gmail.com> - 2013-06-14 10:03 +0100
Re: A certainl part of an if() structure never gets executed. Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-06-14 12:21 +0300
Re: A certainl part of an if() structure never gets executed. Nick the Gr33k <support@superhost.gr> - 2013-06-14 12:44 +0300
Re: A certainl part of an if() structure never gets executed. Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-06-14 15:40 +0300
Re: A certainl part of an if() structure never gets executed. Nick the Gr33k <support@superhost.gr> - 2013-06-14 16:07 +0300
Re: A certainl part of an if() structure never gets executed. Zero Piraeus <schesis@gmail.com> - 2013-06-14 09:48 -0400
Re: A certainl part of an if() structure never gets executed. rusi <rustompmody@gmail.com> - 2013-06-14 07:05 -0700
Re: A certainl part of an if() structure never gets executed. Nick the Gr33k <support@superhost.gr> - 2013-06-14 17:08 +0300
Re: A certainl part of an if() structure never gets executed. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-14 16:31 +0000
Re: A certainl part of an if() structure never gets executed. Nick the Gr33k <support@superhost.gr> - 2013-06-14 19:56 +0300
Re: A certainl part of an if() structure never gets executed. Chris Angelico <rosuav@gmail.com> - 2013-06-15 03:18 +1000
Re: A certainl part of an if() structure never gets executed. Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-06-14 21:17 +0300
Re: A certainl part of an if() structure never gets executed. Larry Hudson <orgnut@yahoo.com> - 2013-06-14 22:27 -0700
Re: A certainl part of an if() structure never gets executed. Nick the Gr33k <support@superhost.gr> - 2013-06-15 11:39 +0300
Re: A certainl part of an if() structure never gets executed. Lele Gaifax <lele@metapensiero.it> - 2013-06-15 11:54 +0200
Re: A certainl part of an if() structure never gets executed. Nick the Gr33k <support@superhost.gr> - 2013-06-15 16:07 +0300
Re: A certainl part of an if() structure never gets executed. Michael Torrie <torriem@gmail.com> - 2013-06-15 09:53 -0600
Re: A certainl part of an if() structure never gets executed. Nick the Gr33k <support@superhost.gr> - 2013-06-15 19:18 +0300
Re: A certainl part of an if() structure never gets executed. Michael Torrie <torriem@gmail.com> - 2013-06-15 11:45 -0600
Re: A certainl part of an if() structure never gets executed. Denis McMahon <denismfmcmahon@gmail.com> - 2013-06-16 06:32 +0000
Re: A certainl part of an if() structure never gets executed. Nick the Gr33k <support@superhost.gr> - 2013-06-16 11:07 +0300
Re: A certainl part of an if() structure never gets executed. Denis McMahon <denismfmcmahon@gmail.com> - 2013-06-16 09:22 +0000
Re: A certainl part of an if() structure never gets executed. Nick the Gr33k <support@superhost.gr> - 2013-06-16 12:59 +0300
Re: A certainl part of an if() structure never gets executed. "R. Michael Weylandt" <michael.weylandt@gmail.com> - 2013-06-16 11:42 +0100
Re: A certainl part of an if() structure never gets executed. Ferrous Cranus <support@superhost.gr> - 2013-06-16 14:06 +0300
Re: A certainl part of an if() structure never gets executed. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-06-16 12:26 +0100
Re: A certainl part of an if() structure never gets executed. YBM <ybmess@nooos.fr.invalid> - 2013-06-16 14:00 +0200
Re: A certainl part of an if() structure never gets executed. "R. Michael Weylandt" <michael.weylandt@gmail.com> - 2013-06-16 13:04 +0100
Re: A certainl part of an if() structure never gets executed. Ferrous Cranus <support@superhost.gr> - 2013-06-16 16:38 +0300
Re: A certainl part of an if() structure never gets executed. "R. Michael Weylandt" <michael.weylandt@gmail.com> - 2013-06-16 19:50 +0100
Re: A certainl part of an if() structure never gets executed. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-06-16 11:52 +0100
Re: A certainl part of an if() structure never gets executed. Denis McMahon <denismfmcmahon@gmail.com> - 2013-06-16 10:51 +0000
Compiling vs interpreting [was Re: A certainl part of an if() structure never gets executed.] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-16 12:07 +0000
Re: Compiling vs interpreting [was Re: A certainl part of an if() structure never gets executed.] Mark Janssen <dreamingforward@gmail.com> - 2013-06-16 12:31 -0700
Re: Compiling vs interpreting [was Re: A certainl part of an if() structure never gets executed.] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-16 20:02 +0000
Re: Compiling vs interpreting [was Re: A certainl part of an if() structure never gets executed.] Chris Angelico <rosuav@gmail.com> - 2013-06-17 08:26 +1000
Re: Compiling vs interpreting [was Re: A certainl part of an if() structure never gets executed.] Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-06-16 23:13 -0400
Re: A certainl part of an if() structure never gets executed. Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-06-16 14:13 +0300
Re: A certainl part of an if() structure never gets executed. Ferrous Cranus <support@superhost.gr> - 2013-06-16 16:47 +0300
Re: A certainl part of an if() structure never gets executed. "R. Michael Weylandt" <michael.weylandt@gmail.com> - 2013-06-16 19:53 +0100
Re: A certainl part of an if() structure never gets executed. Νίκος <support@superhost.gr> - 2013-06-17 08:17 +0300
Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-17 06:51 +0000
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Simpleton <support@superhost.gr> - 2013-06-17 14:34 +0300
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Michael Torrie <torriem@gmail.com> - 2013-06-17 05:58 -0600
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Simpleton <support@superhost.gr> - 2013-06-17 18:50 +0300
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Larry Hudson <orgnut@yahoo.com> - 2013-06-17 23:39 -0700
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-18 07:24 +0000
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Νίκος <support@superhost.gr> - 2013-06-18 11:49 +0300
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-18 09:05 +0000
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Νίκος <support@superhost.gr> - 2013-06-18 12:51 +0300
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Chris Angelico <rosuav@gmail.com> - 2013-06-18 20:22 +1000
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Michael Torrie <torriem@gmail.com> - 2013-06-19 23:16 -0600
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-20 05:48 +0000
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Michael Torrie <torriem@gmail.com> - 2013-06-20 00:01 -0600
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] 88888 Dihedral <dihedral88888@gmail.com> - 2013-06-26 01:18 -0700
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Michael Torrie <torriem@gmail.com> - 2013-06-19 23:44 -0600
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Roel Schroeven <roel@roelschroeven.net> - 2013-06-20 19:19 +0200
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Terry Reedy <tjreedy@udel.edu> - 2013-06-17 10:22 -0400
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Simpleton <support@superhost.gr> - 2013-06-17 18:55 +0300
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Joel Goldstick <joel.goldstick@gmail.com> - 2013-06-17 12:26 -0400
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Benjamin Kaplan <benjamin.kaplan@case.edu> - 2013-06-17 09:23 -0700
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Νίκος <support@superhost.gr> - 2013-06-17 20:17 +0300
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Terry Reedy <tjreedy@udel.edu> - 2013-06-17 18:16 -0400
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-17 23:09 +0000
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Νίκος <support@superhost.gr> - 2013-06-18 02:26 +0300
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-18 00:41 +0000
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Dave Angel <davea@davea.name> - 2013-06-17 21:06 -0400
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-18 02:42 +0000
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Dave Angel <davea@davea.name> - 2013-06-18 00:12 -0400
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-18 06:04 +0000
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-18 02:38 +0000
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-18 02:46 +0000
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-06-17 21:34 -0400
Re: Variables versus name bindings [Re: A certainl part of an if() structure never gets executed.] Marcin Szamotulski <mszamot@gmail.com> - 2013-06-18 04:22 +0100
Re: A certainl part of an if() structure never gets executed. Michael Weylandt <michael.weylandt@gmail.com> - 2013-06-17 07:56 +0100
Re: A certainl part of an if() structure never gets executed. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-16 12:50 +0000
OT: C vs Python terminology (was: A certainl part of an if() structure never gets executed) Andreas Perstinger <andipersti@gmail.com> - 2013-06-16 13:22 +0200
Re: OT: C vs Python terminology Dave Angel <davea@davea.name> - 2013-06-16 08:55 -0400
Re: OT: C vs Python terminology Andreas Perstinger <andipersti@gmail.com> - 2013-06-16 17:02 +0200
Re: OT: C vs Python terminology Dave Angel <davea@davea.name> - 2013-06-16 21:58 -0400
Re: A certainl part of an if() structure never gets executed. "R. Michael Weylandt" <michael.weylandt@gmail.com> - 2013-06-14 09:28 +0100
Re: A certainl part of an if() structure never gets executed. Fábio Santos <fabiosantosart@gmail.com> - 2013-06-14 09:35 +0100
Re: A certainl part of an if() structure never gets executed. Nick the Gr33k <support@superhost.gr> - 2013-06-14 11:44 +0300
Re: A certainl part of an if() structure never gets executed. Chris Angelico <rosuav@gmail.com> - 2013-06-14 18:57 +1000
Re: A certainl part of an if() structure never gets executed. Nick the Gr33k <support@superhost.gr> - 2013-06-14 12:00 +0300
Re: A certainl part of an if() structure never gets executed. Chris Angelico <rosuav@gmail.com> - 2013-06-14 19:12 +1000
Re: A certainl part of an if() structure never gets executed. Nick the Gr33k <support@superhost.gr> - 2013-06-14 12:47 +0300
Re: A certainl part of an if() structure never gets executed. Tim Roberts <timr@probo.com> - 2013-06-15 18:55 -0700
Re: A certainl part of an if() structure never gets executed. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-16 05:09 +0000
Re: A certainl part of an if() structure never gets executed. Nick the Gr33k <support@superhost.gr> - 2013-06-16 11:20 +0300
Re: A certainl part of an if() structure never gets executed. Tim Roberts <timr@probo.com> - 2013-06-18 22:08 -0700
Re: A certainl part of an if() structure never gets executed. Dave Angel <davea@davea.name> - 2013-06-19 01:42 -0400
Re: A certainl part of an if() structure never gets executed. Chris Angelico <rosuav@gmail.com> - 2013-06-19 17:14 +1000
Re: A certainl part of an if() structure never gets executed. Νίκος <support@superhost.gr> - 2013-06-19 10:49 +0300
Re: A certainl part of an if() structure never gets executed. Dave Angel <davea@davea.name> - 2013-06-19 04:06 -0400
Re: A certainl part of an if() structure never gets executed. Chris Angelico <rosuav@gmail.com> - 2013-06-19 18:21 +1000
Re: A certainl part of an if() structure never gets executed. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-19 08:55 +0000
Re: A certainl part of an if() structure never gets executed. Chris Angelico <rosuav@gmail.com> - 2013-06-19 19:14 +1000
Re: A certainl part of an if() structure never gets executed. Grant Edwards <invalid@invalid.invalid> - 2013-06-14 14:38 +0000
Re: A certainl part of an if() structure never gets executed. Fábio Santos <fabiosantosart@gmail.com> - 2013-06-14 10:05 +0100
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