simple integer subclass

samwyse samwyse at gmail.com
Tue Aug 3 02:24:51 CEST 2010


On Aug 2, 6:52 pm, Andreas Pfrengle <a.pfren... at gmail.com> wrote:
> I'm trying to define a subclass of int called int1. An int1-object
> shall behave exactly like an int-object, with the only difference that
> the displayed value shall be value + 1 (it will be used to display
> array indices starting at 1 instead of 0). Right now I have:
>
> class int1(int):
>     def __str__(self):
>         return int.__str__(self + 1)
>
> However, if I calculate with int1 and int- (or other number) objects,
> the result is always coerced to an int (or other number object), e.g:
> a = int1(5)
> b = 5
> print a      # "6"
> print a+b  #"10"
>
> How can I tell int1 to be the "default integer object"? Do I need to
> overload *every* mathematical operation method of int, or is there an
> easier way?

I had a similar problem a few years ago, and couldn't find a solution
then.  The thread from back then may shed some light on your problem.
http://groups.google.com/group/comp.lang.python/browse_thread/thread/10cfe2affc265ac/2ad03b121c1c6489



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