Re: Operator Precedence/Boolean Logic

From	Antoon Pardon <antoon.pardon@rece.vub.ac.be>
Newsgroups	comp.lang.python
Subject	Re: Operator Precedence/Boolean Logic
Date	2016-06-23 13:15 +0200
Message-ID	<mailman.68.1466680570.11516.python-list@python.org> (permalink)
References	(11 earlier) <87oa6sfczf.fsf@elektro.pacujo.net> <576BBFFF.3070504@rece.vub.ac.be> <mailman.67.1466679335.11516.python-list@python.org> <878txwf9w5.fsf@elektro.pacujo.net> <576BC4D4.7030509@rece.vub.ac.be>

Show all headers | View raw

Op 23-06-16 om 12:59 schreef Marko Rauhamaa:
> Antoon Pardon <antoon.pardon@rece.vub.ac.be>:
>
>> Op 23-06-16 om 11:53 schreef Marko Rauhamaa:
>> Maybe something like this:
>>
>> def empty(sq):
>>     try:
>>         iter(sq).next()
>>     except StopIteration:
>>         return False
>>     except:
>>         raise TypeError
>>     else:
>>         return True
> That may or may not be as effective as a boolean check. The point is,
> Python has already declared that __bool__ is the canonical emptiness
> checker. You could even say that it's the principal purpose of the
> __bool__ method.

I think it is wrong to say __bool__ is the canonical emptiness checker.
It can be used for anything where you somehow think it is reasonable
to make a distinction between truthy and falsy. Even when talking
about emptyness doesn't make sense.

The function above at least raises an exception in a lot of cases
where the class provides booly behaviour yet emptyness wouldn't make
sense.

Would it be worth while? That you have to decide for yourself.

-- 
Antoon.

Thread

Operator Precedence/Boolean Logic Elizabeth Weiss <cake240@gmail.com> - 2016-06-21 20:40 -0700
  Re: Operator Precedence/Boolean Logic Ben Finney <ben+python@benfinney.id.au> - 2016-06-22 13:59 +1000
    Re: Operator Precedence/Boolean Logic Elizabeth Weiss <cake240@gmail.com> - 2016-06-22 21:19 -0700
    Re: Operator Precedence/Boolean Logic Elizabeth Weiss <cake240@gmail.com> - 2016-06-22 21:20 -0700
  Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-22 16:02 +1000
  Re: Operator Precedence/Boolean Logic Christian Gollwitzer <auriocus@gmx.de> - 2016-06-22 08:26 +0200
    Re: Operator Precedence/Boolean Logic Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-06-22 10:14 +0300
      Re: Operator Precedence/Boolean Logic Elizabeth Weiss <cake240@gmail.com> - 2016-06-22 21:21 -0700
  Re: Operator Precedence/Boolean Logic Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-22 00:42 -0700
    Re: Operator Precedence/Boolean Logic Larry Hudson <orgnut@yahoo.com> - 2016-06-22 20:12 -0700
      Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-06-23 13:59 +1000
        Re: Operator Precedence/Boolean Logic Elizabeth Weiss <cake240@gmail.com> - 2016-06-22 21:23 -0700
        Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 09:58 +0200
          Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-23 11:16 +0300
            Re: Operator Precedence/Boolean Logic Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-23 01:53 -0700
              Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-23 12:10 +0300
                Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 11:27 +0200
                Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-23 12:53 +0300
                Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 12:54 +0200
                Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-23 13:59 +0300
                Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 13:15 +0200
                Re: Operator Precedence/Boolean Logic Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-06-23 15:05 +0300
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-06-23 22:13 +1000
                Re: Operator Precedence/Boolean Logic Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-23 02:44 -0700
                Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-23 12:57 +0300
                Re: Operator Precedence/Boolean Logic Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-24 22:38 -0700
                Re: Operator Precedence/Boolean Logic Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-06-25 09:46 +0300
            Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 11:01 +0200
          Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-23 19:39 +1000
            Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 12:21 +0200
              Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-06-23 22:37 +1000
                Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 15:24 +0200
                Re: Operator Precedence/Boolean Logic Random832 <random832@fastmail.com> - 2016-06-23 09:26 -0400
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-06-24 02:43 +1000
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-06-24 01:49 +1000
        Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-25 11:56 +0300
      Re: Operator Precedence/Boolean Logic Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-22 21:47 -0700
        Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-06-22 22:00 -0700
        Re: Operator Precedence/Boolean Logic Andreas Röhler <andreas.roehler@online.de> - 2016-06-23 08:34 +0200
          Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-23 09:46 +0300
          Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-23 17:05 +1000
            Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 10:17 +0200
              Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-23 18:48 +1000
                Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 11:23 +0200
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-06-23 21:45 +1000
                Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 14:08 +0200
                Re: Operator Precedence/Boolean Logic Andreas Röhler <andreas.roehler@online.de> - 2016-06-23 14:22 +0200
            Re: Operator Precedence/Boolean Logic Andreas Röhler <andreas.roehler@online.de> - 2016-06-23 10:23 +0200
            Re: Operator Precedence/Boolean Logic Andreas Röhler <andreas.roehler@online.de> - 2016-06-23 10:32 +0200
              Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-23 19:17 +1000
                Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-23 12:46 +0300
                Re: Operator Precedence/Boolean Logic Andreas Röhler <andreas.roehler@online.de> - 2016-06-23 12:19 +0200
                Re: Operator Precedence/Boolean Logic Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-26 11:01 +1200
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-06-29 03:21 -0700
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-06-29 21:06 +1000
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-06-29 23:08 +1000
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-06-29 06:30 -0700
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-06-30 09:40 +1000
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-06-30 09:01 -0700
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-01 03:22 +1000
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-15 22:48 -0700
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-15 22:58 -0700
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-16 19:14 +1000
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-16 20:16 +1000
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-07-16 20:46 +1000
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-16 21:02 +1000
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-07-17 00:26 +1000
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-16 05:33 -0700
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-17 02:27 +1000
                Re: Operator Precedence/Boolean Logic MRAB <python@mrabarnett.plus.com> - 2016-07-16 17:58 +0100
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-16 20:43 -0700
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-07-17 14:05 +1000
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-16 23:44 -0700
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-16 23:59 -0700
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-07-17 17:33 +1000
                Re: Operator Precedence/Boolean Logic Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-07-17 00:44 -0700
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-17 20:04 +1000
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-17 21:02 +1000
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-17 08:00 -0700
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-18 01:58 +1000
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-18 02:01 +1000
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-07-17 03:06 +1000
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-16 05:15 -0700
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-17 02:36 +1000
                Re: Operator Precedence/Boolean Logic Grant Edwards <grant.b.edwards@gmail.com> - 2016-06-29 15:00 +0000
                Re: Operator Precedence/Boolean Logic Jon Ribbens <jon+usenet@unequivocal.eu> - 2016-06-29 15:05 +0000
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-06-30 09:44 +1000
                Re: Operator Precedence/Boolean Logic Andreas Röhler <andreas.roehler@online.de> - 2016-06-23 11:51 +0200
        Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-23 17:20 +1000
        Re: Operator Precedence/Boolean Logic Random832 <random832@fastmail.com> - 2016-06-23 09:18 -0400
      Re: Operator Precedence/Boolean Logic Christian Gollwitzer <auriocus@gmx.de> - 2016-06-23 09:11 +0200
    Re: Operator Precedence/Boolean Logic Elizabeth Weiss <cake240@gmail.com> - 2016-06-22 21:22 -0700
  Fwd: Operator Precedence/Boolean Logic Jorge Gimeno <jlgimeno71@gmail.com> - 2016-06-21 20:56 -0700
  Re: Operator Precedence/Boolean Logic Random832 <random832@fastmail.com> - 2016-06-22 10:10 -0400
  Re: Operator Precedence/Boolean Logic Erik <python@lucidity.plus.com> - 2016-06-22 20:43 +0100

csiph-web