Re: Equivalent code to the bool() built-in function

References	(8 earlier) <4dac97ca$0$10609$742ec2ed@news.sonic.net> <ioip56$btd$1@dough.gmane.org> <BANLkTi=C9nz7zVvBr0nPMiKgO9hkWo2uKA@mail.gmail.com> <mailman.549.1303194413.9059.python-list@python.org> <4dad4b29$0$29984$c3e8da3$5496439d@news.astraweb.com>
Date	2011-04-19 19:00 +1000
Subject	Re: Equivalent code to the bool() built-in function
From	Chris Angelico <rosuav@gmail.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.555.1303203623.9059.python-list@python.org> (permalink)

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On Tue, Apr 19, 2011 at 6:43 PM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> but I don't see how
>
> (arbitrary expression) + (another expression) + ... + (last expression)
>
> can have any guarantees applied. I mean, you can't even guarantee that
> they won't raise an exception. Can you explain what you mean?

What Christian posted isn't something I've often done, but here's
something slightly different that exploits the same
comparisons-return-summable-values concept:

A condition with N subconditions is deemed to be satisfied if a
minimum of M of them are true. This is a general case of the boolean
Or (N = 2, M = 1) and And (N = 2, M = 2), but does not have a direct
equivalent in binary operators. You simply sum the subconditions,
compare against M, and you have your answer.

if (((port<1024) + (!ip.startswith("192.168.")) +
(greylist[ip]>time()) + (++spewcnt>10))>=3) // flag this packet as
suspicious

Contrived example as I don't recall any specifics right now, but this
will pick up any packets where three or more of the conditions are
met. Useful only in fairly specific situations, but I don't know of
any way to do this with just AND/OR/NOT that would be as clear and
simple.

Chris Angelico

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Equivalent code to the bool() built-in function candide <candide@free.invalid> - 2011-04-16 22:24 +0200
  Re: Equivalent code to the bool() built-in function Chris Rebert <clp2@rebertia.com> - 2011-04-16 13:58 -0700
    Re: Equivalent code to the bool() built-in function Ben Finney <ben+python@benfinney.id.au> - 2011-04-17 07:38 +1000
      Re: Equivalent code to the bool() built-in function candide <candide@free.invalid> - 2011-04-17 01:51 +0200
        Re: Equivalent code to the bool() built-in function Chris Rebert <clp2@rebertia.com> - 2011-04-16 17:16 -0700
        Re: Equivalent code to the bool() built-in function Ben Finney <ben+python@benfinney.id.au> - 2011-04-17 12:39 +1000
          Re: Equivalent code to the bool() built-in function candide <candide@free.invalid> - 2011-04-17 10:38 +0200
            Re: Equivalent code to the bool() built-in function Chris Angelico <rosuav@gmail.com> - 2011-04-17 18:46 +1000
              Re: Equivalent code to the bool() built-in function Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-04-18 12:12 +1200
                Re: Equivalent code to the bool() built-in function John Nagle <nagle@animats.com> - 2011-04-18 12:58 -0700
                Re: Equivalent code to the bool() built-in function Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-04-19 12:18 +1200
                Re: Equivalent code to the bool() built-in function Christian Heimes <lists@cheimes.de> - 2011-04-19 03:39 +0200
                Re: Equivalent code to the bool() built-in function Kushal Kumaran <kushal.kumaran+python@gmail.com> - 2011-04-19 11:53 +0530
                Re: Equivalent code to the bool() built-in function Grant Edwards <invalid@invalid.invalid> - 2011-04-19 14:23 +0000
                Re: Equivalent code to the bool() built-in function Jean-Paul Calderone <calderone.jeanpaul@gmail.com> - 2011-04-19 08:43 -0700
                Re: Equivalent code to the bool() built-in function Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-04-20 11:59 +1200
                Re: Equivalent code to the bool() built-in function Chris Angelico <rosuav@gmail.com> - 2011-04-19 16:26 +1000
                Re: Equivalent code to the bool() built-in function Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-04-19 08:43 +0000
                Re: Equivalent code to the bool() built-in function Chris Angelico <rosuav@gmail.com> - 2011-04-19 19:00 +1000
                Re: Equivalent code to the bool() built-in function Westley Martínez <anikom15@gmail.com> - 2011-04-19 06:43 -0700
            Re: Equivalent code to the bool() built-in function Ben Finney <ben+python@benfinney.id.au> - 2011-04-17 19:46 +1000
              Re: Equivalent code to the bool() built-in function candide <candide@free.invalid> - 2011-04-18 01:22 +0200
                Re: Equivalent code to the bool() built-in function Ben Finney <ben+python@benfinney.id.au> - 2011-04-18 09:46 +1000
                Re: Equivalent code to the bool() built-in function Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-04-18 12:08 +1200
                Re: Equivalent code to the bool() built-in function Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-04-18 00:22 +0000
                Re: Equivalent code to the bool() built-in function Chris Angelico <rosuav@gmail.com> - 2011-04-18 10:52 +1000
                Re: Equivalent code to the bool() built-in function Duncan Booth <duncan.booth@invalid.invalid> - 2011-04-18 10:01 +0000
            Re: Equivalent code to the bool() built-in function Daniel Kluev <dan.kluev@gmail.com> - 2011-04-17 21:11 +1100
      Re: Equivalent code to the bool() built-in function Daniel Kluev <dan.kluev@gmail.com> - 2011-04-18 10:45 +1100
        Re: Equivalent code to the bool() built-in function Ben Finney <ben+python@benfinney.id.au> - 2011-04-18 10:36 +1000
      Re: Re: Equivalent code to the bool() built-in function Chris Angelico <rosuav@gmail.com> - 2011-04-18 11:52 +1000
      Re: Re: Equivalent code to the bool() built-in function Dave Angel <davea@ieee.org> - 2011-04-17 21:46 -0400
      Re: Re: Equivalent code to the bool() built-in function Daniel Kluev <dan.kluev@gmail.com> - 2011-04-18 14:16 +1100
      Re: Equivalent code to the bool() built-in function Ned Deily <nad@acm.org> - 2011-04-17 21:40 -0700
      Re: Equivalent code to the bool() built-in function Chris Angelico <rosuav@gmail.com> - 2011-04-18 14:53 +1000
        Re: Equivalent code to the bool() built-in function Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-04-19 12:22 +1200
      Re: Equivalent code to the bool() built-in function Chris Rebert <clp2@rebertia.com> - 2011-04-17 22:49 -0700
        Re: Equivalent code to the bool() built-in function Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-04-18 06:14 +0000
      Re: Equivalent code to the bool() built-in function Chris Angelico <rosuav@gmail.com> - 2011-04-18 16:03 +1000
  Re: Equivalent code to the bool() built-in function Ben Finney <ben+python@benfinney.id.au> - 2011-04-17 07:13 +1000
    Re: Equivalent code to the bool() built-in function candide <candide@free.invalid> - 2011-04-17 01:51 +0200
  Re: Equivalent code to the bool() built-in function Raymond Hettinger <python@rcn.com> - 2011-04-18 01:33 -0700
    Re: Equivalent code to the bool() built-in function candide <candide@free.invalid> - 2011-04-18 11:19 +0200

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