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Re: list storing variables

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On 02/23/2015 07:55 AM, ast wrote:
> hi
>
>>>> a = 2; b = 5
>>>> Li = [a, b]
>>>>
>>>> Li
> [2, 5]
>>>> a=3
>>>> Li
> [2, 5]
>>>>
>
> Ok, a change in a or b doesn't impact Li. This works as expected
>
> 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 ?
>
> I dont need this feature. It is just something I am thinking about.
>
> In C language, there is &A for address of A
>

When you do an "a=3"  you are rebinding a, and that has no connection to 
what's in the list.  If you were to modify the object that a and L1[0] 
share, then yes, the modifications would affect both sides.

However, an int is immutable, so you cannot directly do it.

The simplest approximation to what you're asking is to use a list within 
the list.

a = [42]; b = 65
L1 = [a, b]
a[0] = 99       #this doesn't rebind a, just changes the list
                 # object it is bound to
print(L1)

yields:
[[99], 65]

Clearly, instead of a list, you could use some other mutable object.  In 
fact, you could use something like:

class Dummy(object):
     pass

a = Dummy()
a.value = 12
...


-- 
DaveA

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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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