Re: Closures in leu of pointers?

Date	2013-06-29 08:02 -0600
From	Michael Torrie <torriem@gmail.com>
Subject	Re: Closures in leu of pointers?
References	<2a2072e3-4b12-4ada-872c-1240d2379928@googlegroups.com> <mailman.3984.1372500107.3114.python-list@python.org> <bc798729-f935-448d-9d62-c409b2d12e76@googlegroups.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.3989.1372514543.3114.python-list@python.org> (permalink)

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On 06/29/2013 05:21 AM, cts.private.yahoo@gmail.com wrote:
> Thank you.  You reminded me of the (weak) workaround of using arrays
> and confirmed my suspicion that I although I can read the variable, I
> won't be able to write to it.  I still don't understand why not,
> though...

The real problem here is that you don't understand how python variables
work.  And in fact, python does not have variables.  It has names that
bind to objects.  If you assign a value to a name, you're not
overwriting a variable, you're rebinding a name to a new object in the
default scope (unless it's declared global, or nonlocal in python 3, the
latter I assume uses the same scope in which it was first declared, but
I could be wrong).  Since the name is in the local scope, the original
name in the caller's scope is still bound to its original object.

Furthermore, most primitive objects in python (strings, ints, etc) are
immutable, which means they can *never change*.  "Writing" to a variable
simply dereferences the old object (which may still be referenced in the
caller's scope) and creates a new object and binds it to the name.

A list is mutable, which is why it's one solution to emulate a variable.

> As for python 3 ... "nonlocal"?  I see I'm not alone in picking
> obnoxious names ...

nonlocal at least has meaning.

Thread

Closures in leu of pointers? cts.private.yahoo@gmail.com - 2013-06-29 02:34 -0700
  Re: Closures in leu of pointers? Fábio Santos <fabiosantosart@gmail.com> - 2013-06-29 10:42 +0100
  Re: Closures in leu of pointers? Peter Otten <__peter__@web.de> - 2013-06-29 12:01 +0200
    Re: Closures in leu of pointers? cts.private.yahoo@gmail.com - 2013-06-29 04:21 -0700
      Re: Closures in leu of pointers? cts.private.yahoo@gmail.com - 2013-06-29 04:44 -0700
        Re: Closures in leu of pointers? Peter Otten <__peter__@web.de> - 2013-06-29 14:12 +0200
          Re: Closures in leu of pointers? cts.private.yahoo@gmail.com - 2013-06-29 05:26 -0700
            Re: Closures in leu of pointers? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-06-29 15:37 +0100
              Re: Closures in leu of pointers? cts.private.yahoo@gmail.com - 2013-06-29 07:48 -0700
        Re: Closures in leu of pointers? Michael Torrie <torriem@gmail.com> - 2013-06-29 07:56 -0600
        Re: Closures in leu of pointers? Michael Torrie <torriem@gmail.com> - 2013-06-29 12:36 -0600
      Re: Closures in leu of pointers? Michael Torrie <torriem@gmail.com> - 2013-06-29 08:02 -0600
      Re: Closures in leu of pointers? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-06-29 19:02 +0200
        Re: Closures in leu of pointers? rusi <rustompmody@gmail.com> - 2013-06-29 10:33 -0700
          Re: Closures in leu of pointers? cts.private.yahoo@gmail.com - 2013-06-29 11:37 -0700
            Re: Closures in leu of pointers? Michael Torrie <torriem@gmail.com> - 2013-06-29 12:58 -0600
            Re: Closures in leu of pointers? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-29 18:59 +0000
        Re: Closures in leu of pointers? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-29 18:51 +0000
          Re: Closures in leu of pointers? Michael Torrie <torriem@gmail.com> - 2013-06-29 13:04 -0600
          Re: Closures in leu of pointers? rusi <rustompmody@gmail.com> - 2013-06-29 12:11 -0700
      Re: Closures in leu of pointers? Michael Torrie <torriem@gmail.com> - 2013-06-29 12:35 -0600
        Re: Closures in leu of pointers? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-29 19:19 +0000
          Re: Closures in leu of pointers? Tim Chase <tim@thechases.com> - 2013-06-29 14:42 -0500
            Re: Closures in leu of pointers? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-30 01:41 +0000
          Re: Closures in leu of pointers? Joshua Landau <joshua.landau.ws@gmail.com> - 2013-06-29 21:02 +0100
          Re: Closures in leu of pointers? Michael Torrie <torriem@gmail.com> - 2013-06-29 16:02 -0600
      Re: Closures in leu of pointers? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-29 18:45 +0000
        Re: Closures in leu of pointers? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-29 19:00 +0000
        Re: Closures in leu of pointers? cts.private.yahoo@gmail.com - 2013-06-29 12:20 -0700
          Re: Closures in leu of pointers? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-29 19:33 +0000
            Re: Closures in leu of pointers? cts.private.yahoo@gmail.com - 2013-06-29 12:34 -0700
            Re: Closures in leu of pointers? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-29 13:47 -0600
            Re: Closures in leu of pointers? Terry Reedy <tjreedy@udel.edu> - 2013-06-29 16:53 -0400
              Re: Closures in leu of pointers? rusi <rustompmody@gmail.com> - 2013-06-30 01:56 -0700
                Re: Closures in leu of pointers? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-30 11:22 +0000
                Re: Closures in leu of pointers? rusi <rustompmody@gmail.com> - 2013-06-30 04:42 -0700
            Re: Closures in leu of pointers? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-29 15:21 -0600
              Re: Closures in leu of pointers? cts.private.yahoo@gmail.com - 2013-06-29 14:30 -0700
            Re: Closures in leu of pointers? Terry Reedy <tjreedy@udel.edu> - 2013-06-30 00:32 -0400
            Re: Closures in leu of pointers? Chris Angelico <rosuav@gmail.com> - 2013-06-30 15:08 +1000
              Re: Closures in leu of pointers? rusi <rustompmody@gmail.com> - 2013-06-30 00:36 -0700
            Re: Closures in leu of pointers? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-29 23:46 -0600
              Re: Closures in leu of pointers? alex23 <wuwei23@gmail.com> - 2013-07-01 14:57 +1000
              Re: Closures in leu of pointers? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-01 07:36 +0000
            Re: Closures in leu of pointers? Chris Angelico <rosuav@gmail.com> - 2013-06-30 15:59 +1000
            Re: Closures in leu of pointers? Terry Reedy <tjreedy@udel.edu> - 2013-06-30 02:11 -0400
            Re: Closures in leu of pointers? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-30 00:24 -0600
          Re: Closures in leu of pointers? Michael Torrie <torriem@gmail.com> - 2013-06-29 16:03 -0600
      Re: Closures in leu of pointers? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-29 13:23 -0600
      Re: Closures in leu of pointers? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-06-30 12:07 +0200
      Re: Closures in leu of pointers? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-30 11:13 -0600
      Re: Closures in leu of pointers? Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-30 11:18 -0600

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