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Usefulness of subclassing builtin number types

Gerhard Häring gerhard.haering at gmx.de
Sun Dec 15 18:28:28 EST 2002 
* Skip Montanaro <skip at pobox.com> [2002-12-15 17:01 -0600]:
>     > And I want (of course) that this subclassing is 'sticky', so if I do a:
>     >     x = MyInt(25)
>     >     x *= 2
> 
>     > I want 'x' to stay of the class MyInt.
> 
> This works for me:
> 
>     class MyInt(int):
>         def __imul__(self, other):
>             return MyInt(self*other)

The *= was only meant as an example. I want the objects of my class to
keep being objects of my class for all artithmetic operations. At least
as long as both operands are MyInts.

My complaint was that I have to do this for almost all methods of 'int'.
There's little gain here compared to just implementing the number
protocol.

And as Martin pointed out, there's the question if I really want to try
casting to my int subclass if isinstance(other, float), for example.

Gerhard
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