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The binding operator, and what gets bound to what (was: About Modifying Globals)

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Steven D'Aprano <steve+comp.lang.python@pearwood.info> writes:

> LJ wrote:
>
> > def gt(l):
> >    a["1"] = a["1"] | set([l])
>
> The difference between this example and your second one:
>
> > def gt2(l):
> >    b=b+l
>
>
> is that the second is a "binding operation" and the first is not.

I disagree; they're both binding operations (and they both use the
binding operator ‘=’ to express this).

The difference between the two is: what reference is being bound?

* In the first example, the reference is ‘a["1"]’.

  That reference is re-bound to a different object; whatever object it
  was previously bound to is forgotten.

* In the second example, the reference is ‘b’.

  That reference is re-bound to a different object; whatever object it
  was previously bound to is forgotten.

So, both of them bind (or re-bind) a reference to an object. The only
difference between the operations is the parameters.

-- 
 \      “People always ask me, ‘Where were you when Kennedy was shot?’ |
  `\                        Well, I don't have an alibi.” —Emo Philips |
_o__)                                                                  |
Ben Finney

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Thread

About Modifying Globals LJ <luisjosenovoa@gmail.com> - 2014-12-04 12:09 -0800
  Re: About Modifying Globals Chris Angelico <rosuav@gmail.com> - 2014-12-05 07:22 +1100
  Re: About Modifying Globals Ian Kelly <ian.g.kelly@gmail.com> - 2014-12-04 13:21 -0700
  Re: About Modifying Globals Dave Angel <davea@davea.name> - 2014-12-04 18:54 -0500
  Re: About Modifying Globals Chris Angelico <rosuav@gmail.com> - 2014-12-05 10:58 +1100
  Re: About Modifying Globals Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-05 13:09 +1100
    The binding operator, and what gets bound to what (was: About Modifying Globals) Ben Finney <ben+python@benfinney.id.au> - 2014-12-05 16:36 +1100
      Re: The binding operator, and what gets bound to what (was: About Modifying Globals) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-05 20:53 +1100
        Re: The binding operator, and what gets bound to what (was: About Modifying Globals) Chris Angelico <rosuav@gmail.com> - 2014-12-05 21:03 +1100
          Re: The binding operator, and what gets bound to what (was: About Modifying Globals) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-05 23:26 +1100
            Re: The binding operator, and what gets bound to what (was: About Modifying Globals) Chris Angelico <rosuav@gmail.com> - 2014-12-05 23:42 +1100
        Re: The binding operator, and what gets bound to what Ned Batchelder <ned@nedbatchelder.com> - 2014-12-05 07:06 -0500
          Re: The binding operator, and what gets bound to what Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-05 23:34 +1100
            Re: The binding operator, and what gets bound to what Chris Angelico <rosuav@gmail.com> - 2014-12-05 23:48 +1100
            Re: The binding operator, and what gets bound to what Ned Batchelder <ned@nedbatchelder.com> - 2014-12-05 07:56 -0500
  Re: About Modifying Globals "shiyao.ma" <i@introo.me> - 2014-12-05 10:53 +0800

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