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Groups > comp.lang.python > #48215
| From | Grant Edwards <invalid@invalid.invalid> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: Eval of expr with 'or' and 'and' within |
| Date | 2013-06-14 19:36 +0000 |
| Organization | PANIX Public Access Internet and UNIX, NYC |
| Message-ID | <kpfrbt$sd2$3@reader1.panix.com> (permalink) |
| References | <kpep0v$spl$8@news.ntua.gr> <51BB44E5.9010201@gmail.com> <mailman.3317.1371228471.3114.python-list@python.org> <kpfi92$107f$1@news.ntua.gr> |
On 2013-06-14, Nick the Gr33k <support@superhost.gr> wrote:
> On 14/6/2013 7:47 ????, Benjamin Kaplan wrote:
> In an "and" clause,
>> python returns the first false value or the last value, because that
>> will evaluate to the correct Boolean value. In an "or" clause, python
>> returns the first true value or the last value. When Python finally got
>> a Boolean type, no one wanted to break backwards compatibility for this.
>
>
> This is exactly what i dont understand and thats why i keep asking and
> people call me an idiot. I just dont understand why it behaves like that.
>
> Why return first or last value?
There are cases where it's useful not only to know wether an
expression was True or False, but _why_ it was true or false.
> because that will evaluate to the correct Boolean value ????
Yes. All values in Pyton have a "truthness" and you can be guaranteed
that
if A or B or C:
will behave exactly the same way whether the "or" operator returns
True or it returns one of it's operands.
--
Grant Edwards grant.b.edwards Yow! Where do your SOCKS
at go when you lose them in
gmail.com th' WASHER?
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Eval of expr with 'or' and 'and' within Nick the Gr33k <support@superhost.gr> - 2013-06-14 12:50 +0300
Re: Eval of expr with 'or' and 'and' within Fábio Santos <fabiosantosart@gmail.com> - 2013-06-14 11:03 +0100
Re: Eval of expr with 'or' and 'and' within Robert Kern <robert.kern@gmail.com> - 2013-06-14 11:14 +0100
Re: Eval of expr with 'or' and 'and' within Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-14 16:09 +0000
Re: Eval of expr with 'or' and 'and' within rusi <rustompmody@gmail.com> - 2013-06-14 09:21 -0700
Re: Eval of expr with 'or' and 'and' within Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-06-14 20:03 +0200
Re: Eval of expr with 'or' and 'and' within rusi <rustompmody@gmail.com> - 2013-06-14 11:37 -0700
Re: Eval of expr with 'or' and 'and' within Joshua Landau <joshua.landau.ws@gmail.com> - 2013-06-14 19:47 +0100
Re: Eval of expr with 'or' and 'and' within alex23 <wuwei23@gmail.com> - 2013-06-14 23:50 -0700
Re: Eval of expr with 'or' and 'and' within Nick the Gr33k <support@superhost.gr> - 2013-06-15 10:04 +0300
Re: Eval of expr with 'or' and 'and' within Denis McMahon <denismfmcmahon@gmail.com> - 2013-06-15 07:49 +0000
Re: Eval of expr with 'or' and 'and' within Nick the Gr33k <support@superhost.gr> - 2013-06-15 10:59 +0300
Re: Eval of expr with 'or' and 'and' within Grant Edwards <invalid@invalid.invalid> - 2013-06-14 14:49 +0000
Re: Eval of expr with 'or' and 'and' within Nick the Gr33k <support@superhost.gr> - 2013-06-14 18:16 +0300
Re: Eval of expr with 'or' and 'and' within Nobody <nobody@nowhere.com> - 2013-06-14 17:42 +0100
Re: Eval of expr with 'or' and 'and' within Grant Edwards <invalid@invalid.invalid> - 2013-06-14 19:30 +0000
Re: Eval of expr with 'or' and 'and' within Nobody <nobody@nowhere.com> - 2013-06-15 00:02 +0100
Re: Eval of expr with 'or' and 'and' within Nick the Gr33k <support@superhost.gr> - 2013-06-15 10:57 +0300
Re: Eval of expr with 'or' and 'and' within Michael Torrie <torriem@gmail.com> - 2013-06-14 10:29 -0600
Re: Eval of expr with 'or' and 'and' within Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-14 16:49 +0000
Re: Eval of expr with 'or' and 'and' within Michael Torrie <torriem@gmail.com> - 2013-06-14 11:28 -0600
Re: Eval of expr with 'or' and 'and' within MRAB <python@mrabarnett.plus.com> - 2013-06-14 18:49 +0100
Re: Eval of expr with 'or' and 'and' within Chris Angelico <rosuav@gmail.com> - 2013-06-15 03:56 +1000
Re: Eval of expr with 'or' and 'and' within Grant Edwards <invalid@invalid.invalid> - 2013-06-14 19:33 +0000
Re: Eval of expr with 'or' and 'and' within Chris Angelico <rosuav@gmail.com> - 2013-06-15 09:56 +1000
Re: Eval of expr with 'or' and 'and' within Nobody <nobody@nowhere.com> - 2013-06-15 00:09 +0100
Re: Eval of expr with 'or' and 'and' within Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-15 01:34 +0000
Re: Eval of expr with 'or' and 'and' within Cameron Simpson <cs@zip.com.au> - 2013-06-15 12:03 +1000
NANs [was Re: Eval of expr with 'or' and 'and' within] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-15 04:22 +0000
Re: Eval of expr with 'or' and 'and' within Chris Angelico <rosuav@gmail.com> - 2013-06-15 12:21 +1000
Re: Eval of expr with 'or' and 'and' within Nobody <nobody@nowhere.com> - 2013-06-15 00:06 +0100
Re: Eval of expr with 'or' and 'and' within MRAB <python@mrabarnett.plus.com> - 2013-06-15 01:26 +0100
Re: Eval of expr with 'or' and 'and' within Benjamin Kaplan <benjamin.kaplan@case.edu> - 2013-06-14 09:47 -0700
Re: Eval of expr with 'or' and 'and' within Nick the Gr33k <support@superhost.gr> - 2013-06-14 20:01 +0300
Re: Eval of expr with 'or' and 'and' within Robert Kern <robert.kern@gmail.com> - 2013-06-14 18:27 +0100
Re: Eval of expr with 'or' and 'and' within Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-06-14 22:05 +0300
Re: Eval of expr with 'or' and 'and' within Grant Edwards <invalid@invalid.invalid> - 2013-06-14 19:36 +0000
Re: Eval of expr with 'or' and 'and' within Cameron Simpson <cs@zip.com.au> - 2013-06-15 10:14 +1000
Re: Eval of expr with 'or' and 'and' within Nick the Gr33k <support@superhost.gr> - 2013-06-15 11:20 +0300
Re: Eval of expr with 'or' and 'and' within Lele Gaifax <lele@metapensiero.it> - 2013-06-15 11:48 +0200
Re: Eval of expr with 'or' and 'and' within Nick the Gr33k <support@superhost.gr> - 2013-06-15 16:24 +0300
Re: Eval of expr with 'or' and 'and' within Nick the Gr33k <support@superhost.gr> - 2013-06-15 16:28 +0300
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