[Python-Dev] inheriting basic types more efficiently (original) (raw)

"Martin v. Löwis" martin at v.loewis.de
Thu Apr 27 21:46:18 CEST 2006

Dennis Heuer wrote:

The real misunderstanding lies somewhere else. I thought that the bitarray's instance would have more control over the long type's instance, like with the mutable types. I thought that the long type's superclass would provide methods similar to setitem that would allow the bitarray instance to even refresh (or substitute) the long instance in place. The result would be a freshly created long instance substituting the old one. But the immuntable types do not offer such a feature because one cannot substitute the long instance without breaking the bitarray instance too.

Maybe that's the misunderstanding: but then you are still left with the mis-design. Even if long was mutable, or even if you used a mutable type as the base type (such as array.array), you still shouldn't inherit from it - these types are not in an "is-a" relationship.

Regards, Martin

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