[Tutor] Variable Modification in a class

[Mehta, Anish]

But if i quote it from the same example in C here:

typedef struct ab
{
        int a;
        int b;
}AB;

main()
{
   AB b;
   AB c;

   b.a = 5;
   b.b = 10;

   c = b;

   c.a = 30;
   c.b = 40;

   printf("AB values %d %d\n", b.a, b.b);
   printf("New values %d %d\n", c.a, c.b);
}

The output is:

AB values 5 10
New values 30 40

Where does the difference lie between this code and its equivalent 
python code. Where i am going wrong in my python code for this type of 
code in C

Waiting for reply

Thanks for responding

Regards

Tom Jenkins wrote:

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> Mehta, Anish wrote:
> | Hello!
> |
> | I am having a problem in tackling the variables in the class.
> |
> | class ab:
> |    def __init__(self):
> |        self.a = None
> |        self.b = None
> |
> | def func(ab):
> |    b = ab
> |    c = ab
> |
> |    b.a = 5
> |    b.b = 10
> |
> |    c = b
> |    c.a = 30
> |    c.b = 40
> |
> |    print b.a, b.b
> |    print c.a, c.b
> |    t = func(ab())
> |
> |
> | Output is
> | 30 40
> | 30 40
> |
> | I want the output to be
> | 5 10
> | 30 40
> |
> | I mean every instance should modify its own set of variables not the
> | variables of the other instances of the class. The output of the set of
> | variables of b should not be affected by modifying those variables by
> | another instance of the same class.
> |
>
> That is completely correct.  However you are not modifying different
> instances of the class, you are modifying the same instances...
>
> | def func(ab):
> |    b = ab
> |    c = ab
>
> b and c both reference instance ab;
>
> |    b.a = 5
> |    b.b = 10
> |
>
> make changes to instance referenced by b (and since b and c reference
> same instance, c as well)
>
> |    c = b
>
> even if above you hadn't explicitly made b and c reference the same
> instance, here you are again saying c should reference the same instance
> as b
>
> |    c.a = 30
> |    c.b = 40
>
>
> make changes to instance referenced by c (and since b and c reference
> same instance, b as well)
>
> what i _think_ you want is...
>
> def func(ab):
> ~   b = ab()
> ~   c = ab()
>
> ~   b.a = 5
> ~   b.b = 10
>
> ~   c.a = 30
> ~   c.b = 40
>
> ~   print b.a, b.b
> ~   print c.a, c.b
> t = func(ab)
>
> - --
> Tom Jenkins
> devIS - Development Infostructure
> http://www.devis.com
>
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