simple integer subclass

Andreas Pfrengle a.pfrengle at gmail.com
Tue Aug 3 12:15:56 CEST 2010


On 3 Aug., 03:22, Carl Banks <pavlovevide... at gmail.com> wrote:>
> You are creating an object that differs from a built-in, int, in a
> highly misleading way that only makes sense in a very limited context,
> and this object's modified behavior gives no clue that it's been
> modified in such as way.  (That is, it's not possible to tell if the
> object's not a regular int just by looking at __str__()'s return
> value.)  To make matters worse, you want to program this object to
> coerce other integers, so there's a risk of these objects escaping
> from the context where they make sense.
>
> This is just a bad idea.  The type is not the place to implement
> behavior that makes sense only in a limited context.  Instead, do
> something like this:
>
> print "Item %d is %s." % (i+1, s[i])

I see your concerns. I started with the approach to add +1 directly
before displaying the int. However, since there are some variables
that shall be displayed normally and others that are indices I want to
show starting at 1, I thought the easiest way would be to define a
type that does the job, then I would only need to define it once and
not take care everywhere whether I have a normal variable or a
displayed index.
Thinking about it, it might really be dangerous to coerce always to
int1, since sometimes I might want a normal int as result (I can't
tell yet for sure).
I'm just thinking about only overloading the operations if the int1 is
on the left-hand side (so __op__ coerces to int1, while __rop__
doesn't). This would make operations non-commutative - but I also
would need to put more brains in every calculation, which could
finally take more effort than only "upgrading" the display :-???
Seems I end up with your suggestion - if noone else has an idea ;-)

The application will be a browsergame, and most gamers start counting
at 1, so they would probably wonder about a "level 0 item" ;-)
If there didn't already exist lots of code, I would redesign the whole
data-structure - I think that's "lessons learned" for the next project
-.-



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