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

References	<4da9fb0b$0$13696$426a74cc@news.free.fr>
Date	2011-04-16 13:58 -0700
Subject	Re: Equivalent code to the bool() built-in function
From	Chris Rebert <clp2@rebertia.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.442.1302987518.9059.python-list@python.org> (permalink)

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On Sat, Apr 16, 2011 at 1:24 PM, candide <candide@free.invalid> wrote:
> Consider the following code :
>
> # --------------------------------------
> def bool_equivalent(x):
>    return True if x else False
>
>
> # testing ...
>
> def foo(x):
>    return 10*x
>
> class C:
>    pass
>
> for x in [42, ("my","baby"), "baobab", max, foo, C] + [None, 0, "", [],
> {},()]:
>    print bool(x)==bool_equivalent(x)
> # --------------------------------------
>
>
> Is the bool_equivalent() function really equivalent to the bool() built-in
> function ?

The ternary operator, if-statement, and `while` all do the equivalent
of an implicit bool() on their condition, so bool_equivalent() will
always give the same result as bool() because it's indeed using the
moral equivalent of bool() behind the scenes.
That is, `True if x else False` conceptually gets compiled down to
`True if bool(x) == 1 else False` (but without doing a run-time lookup
of "bool").

Cheers,
Chris
--
http://blog.rebertia.com

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Thread

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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