Re: Implicit conversion to boolean in if and while statements

Newsgroups	comp.lang.python
Date	2013-02-12 18:43 -0800
References	(19 earlier) <mailman.1641.1360586431.2939.python-list@python.org> <43b37855-1d4d-4b16-ac83-115754bc9346@googlegroups.com> <aa3a5678-f98b-4b71-a510-0dddfb07998b@googlegroups.com> <mailman.1687.1360648522.2939.python-list@python.org> <0c9bb6fd-b995-4a54-ba2e-4d446072a948@googlegroups.com>
Subject	Re: Implicit conversion to boolean in if and while statements
From	88888 Dihedral <dihedral88888@googlemail.com>
Message-ID	<mailman.1732.1360723431.2939.python-list@python.org> (permalink)

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Rick Johnson於 2013年2月13日星期三UTC+8上午1時48分07秒寫道：
> 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. 
> 
> 

>>> a1=[1,2,3]
>>> tuple1=(a1,4,5,6)
>>> tuple1
([1, 2, 3], 4, 5, 6)
>>> a1=[1,2]
>>> tuple1
([1, 2, 3], 4, 5, 6)
>>> 

Yes, a tuple of constant objects is still not clear. 


> 
> 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.

Thread

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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