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Re: list storing variables

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"ast" <nomail@invalid.com> writes:

> Ok, a change in a or b doesn't impact Li. This works as expected

Because a container stores references to objects. The other references
(such as names) that object might have are not stored.

> Is there a way to define a container object able to store some
> variables so that a change of a variable make a change in this object
> content ?

As has been pointed out, Python does not have “variables” in the sense
of a named box containing a value.

What Python does have is a mapping type. You can store a key → value
mapping for each value you want to reference later.

    >>> a = 2; b = 5
    >>> foo = {'a': a, 'b': b}
    >>> foo
    {'b': 5, 'a': 2}
    >>> foo['a'] = 3
    >>> foo
    {'b': 5, 'a': 3}

You appear, though, to want this to somehow automatically track the
changes in name bindings. No, there's no way to do that except
explicitly coding it yourself.

> In C language, there is &A for address of A

There is no “address of a value” concept in Python. You access a value
by some reference, either a name or an item in a collection. When a
reference changes to reference some different value, other references
are not affected.

-- 
 \        “All opinions are not equal. Some are a very great deal more |
  `\   robust, sophisticated, and well supported in logic and argument |
_o__)                                     than others.” —Douglas Adams |
Ben Finney

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Thread

list storing variables "ast" <nomail@invalid.com> - 2015-02-23 13:55 +0100
  Re: list storing variables Dave Angel <davea@davea.name> - 2015-02-23 08:24 -0500
  Re: list storing variables Marko Rauhamaa <marko@pacujo.net> - 2015-02-23 15:49 +0200
  Re: list storing variables Peter Pearson <pkpearson@nowhere.invalid> - 2015-02-23 17:35 +0000
    Re: list storing variables Marko Rauhamaa <marko@pacujo.net> - 2015-02-23 20:22 +0200
      Re: list storing variables Peter Otten <__peter__@web.de> - 2015-02-23 19:41 +0100
        Re: list storing variables Marko Rauhamaa <marko@pacujo.net> - 2015-02-23 21:06 +0200
          Re: list storing variables Chris Angelico <rosuav@gmail.com> - 2015-02-24 06:17 +1100
            Re: list storing variables Marko Rauhamaa <marko@pacujo.net> - 2015-02-23 22:25 +0200
          Re: list storing variables Ian Kelly <ian.g.kelly@gmail.com> - 2015-02-23 12:29 -0700
            Re: list storing variables Marko Rauhamaa <marko@pacujo.net> - 2015-02-23 22:38 +0200
  Re: list storing variables Ben Finney <ben+python@benfinney.id.au> - 2015-02-24 09:03 +1100
    Re: list storing variables Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-02-24 13:24 +1100
      Re: list storing variables Marko Rauhamaa <marko@pacujo.net> - 2015-02-24 10:18 +0200

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