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Re: Implicit conversion to boolean in if and while statements

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Subject Re: Implicit conversion to boolean in if and while statements
From Rick Johnson <rantingrickjohnson@gmail.com>
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On Monday, February 11, 2013 11:55:19 PM UTC-6, Chris Angelico wrote:
> On Tue, Feb 12, 2013 at 12:06 PM, 88888 Dihedral wrote:
> > A permanently mutated list is a tuple of constant objects.
>
> I nominate this line as "bemusing head-scratcher of the week".

Actually the statement is fact IF you can grok it through the eyes of clarity.

"A permanently mutated list..."

A list that has been mutated permanently, that is, it cannot be changed back into a list. psst: i have a sneaking suspicion that he his referring to tuples, let's see.

"...is a tuple..."

Ha! Well in Python the immutable sequence type /is/ a tuple after all.

"...of constant objects..."

The tuple contains objects, and it's objects will maintain a constant ordering (relatively in tuple structure) until until the tuple's death. 

Your confusion may stem from interpreting "constant" as the CS term "CONSTANT"[1]; whereby the objects in the tuple are programming CONSTANTS, that is, unable to change. But in reality, although a tuple (bka:StaticList) cannot expand to add more objects, or shrink to eject existing objects, the objects themselves CAN change their own internal state WITHOUT disrupting the immutable harmony of the tuple. 

Observe:
    
py> class Foo(object):
	pass
py> foo = Foo()
py> t = (1,'1', foo)
py> t
(1, '1', <__main__.Foo object at 0x0267BF50>)
py> t[-1].bar = "abc"
py> t
(1, '1', <__main__.Foo object at 0x0267BF50>)

Or by expanding a list

py> t = (1,2,3)
py> t = t+([],)
py> t
(1, 2, 3, [])
py> t[-1].append('circus')
py> t
(1, 2, 3, ['circus'])

[1] Which is an unfortunate side-effect of polysemy and compounded exponentially by naive (and sometimes a purely malevolent intent when) transformation of words into esoteric problem domains.

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Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-07 22:16 -0800
  Re: Implicit conversion to boolean in if and while statements Michael Torrie <torriem@gmail.com> - 2013-02-07 23:27 -0700
    Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-07 22:32 -0800
    Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-07 22:32 -0800
  Re: Implicit conversion to boolean in if and while statements Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-09 02:16 +1100
    Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-08 09:48 -0800
      Re: Implicit conversion to boolean in if and while statements Roy Smith <roy@panix.com> - 2013-02-08 12:58 -0500
      Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-08 11:58 -0800
        Re: Implicit conversion to boolean in if and while statements Chris Angelico <rosuav@gmail.com> - 2013-02-09 11:05 +1100
          Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-08 16:49 -0800
            Re: Implicit conversion to boolean in if and while statements Chris Angelico <rosuav@gmail.com> - 2013-02-09 12:17 +1100
              Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-09 20:54 -0800
                Re: Implicit conversion to boolean in if and while statements Chris Angelico <rosuav@gmail.com> - 2013-02-10 16:04 +1100
                Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-11 04:28 -0800
                Re: Implicit conversion to boolean in if and while statements Chris Angelico <rosuav@gmail.com> - 2013-02-11 23:50 +1100
                Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-11 05:28 -0800
                Re: Implicit conversion to boolean in if and while statements Chris Angelico <rosuav@gmail.com> - 2013-02-12 00:52 +1100
                Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-11 20:24 -0800
                Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-11 20:24 -0800
                Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-11 05:28 -0800
                Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-11 04:28 -0800
              Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-09 20:54 -0800
            Re: Implicit conversion to boolean in if and while statements Ian Kelly <ian.g.kelly@gmail.com> - 2013-02-08 18:29 -0700
            Re: Implicit conversion to boolean in if and while statements Chris Angelico <rosuav@gmail.com> - 2013-02-09 16:01 +1100
              Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-09 20:26 -0800
                Re: Implicit conversion to boolean in if and while statements Chris Angelico <rosuav@gmail.com> - 2013-02-10 15:50 +1100
                Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-10 18:09 -0800
                Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-10 18:09 -0800
                Re: Implicit conversion to boolean in if and while statements Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-10 22:37 +1100
                Re: Implicit conversion to boolean in if and while statements Roy Smith <roy@panix.com> - 2013-02-10 09:45 -0500
                Re: Implicit conversion to boolean in if and while statements Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2013-02-10 18:06 +0100
                Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-11 04:18 -0800
                Re: Implicit conversion to boolean in if and while statements Chris Angelico <rosuav@gmail.com> - 2013-02-11 23:40 +1100
                Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-11 05:13 -0800
                Re: Implicit conversion to boolean in if and while statements Chris Angelico <rosuav@gmail.com> - 2013-02-12 00:35 +1100
                Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-11 20:00 -0800
                Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-11 20:00 -0800
                Re: Implicit conversion to boolean in if and while statements 88888 Dihedral <dihedral88888@googlemail.com> - 2013-02-11 17:06 -0800
                Re: Implicit conversion to boolean in if and while statements Chris Angelico <rosuav@gmail.com> - 2013-02-12 16:55 +1100
                Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-12 09:48 -0800
                Re: Implicit conversion to boolean in if and while statements Chris Angelico <rosuav@gmail.com> - 2013-02-13 08:24 +1100
                Re: Implicit conversion to boolean in if and while statements 88888 Dihedral <dihedral88888@googlemail.com> - 2013-02-12 18:43 -0800
                Re: Implicit conversion to boolean in if and while statements 88888 Dihedral <dihedral88888@googlemail.com> - 2013-02-12 18:43 -0800
                Re: Implicit conversion to boolean in if and while statements Ian Kelly <ian.g.kelly@gmail.com> - 2013-02-15 13:12 -0700
                Re: Implicit conversion to boolean in if and while statements Chris Angelico <rosuav@gmail.com> - 2013-02-16 11:12 +1100
                Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-12 09:48 -0800
                Re: Implicit conversion to boolean in if and while statements 88888 Dihedral <dihedral88888@googlemail.com> - 2013-02-11 17:06 -0800
                Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-11 05:13 -0800
                Re: Implicit conversion to boolean in if and while statements Serhiy Storchaka <storchaka@gmail.com> - 2013-02-15 21:09 +0200
              Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-09 20:26 -0800
          Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-08 16:49 -0800
        Re: Implicit conversion to boolean in if and while statements Ian Kelly <ian.g.kelly@gmail.com> - 2013-02-08 18:06 -0700
          Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-09 22:25 -0800
          Re: Implicit conversion to boolean in if and while statements Rick Johnson <rantingrickjohnson@gmail.com> - 2013-02-09 22:25 -0800
      Re: Implicit conversion to boolean in if and while statements Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-09 14:16 +1100
        Re: Implicit conversion to boolean in if and while statements Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-02-09 15:36 -0500
      Re: Implicit conversion to boolean in if and while statements Mark Janssen <dreamingforward@gmail.com> - 2013-02-11 21:12 -0800

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