[Python-ideas] method decorators @final and @override in Python 2.4

Scott David Daniels Scott.Daniels at Acm.Org
Sat Mar 28 19:32:19 CET 2009

Péter Szabó wrote:
> Hi,
> If Python had method decorators @final (meaning: it is an error to
> override this method in any subclass) and @override (meaning: it is an
> error not having this method in a superclass), I would use them in my
> projects (some of them approaching 20 000 lines of Python code) and
> I'll feel more confident writing object-oriented Python code. Java
> already has similar decorators or specifiers. Do you think it is a
> good idea to have these in Python?
> I've created a proof-of-concept implementation, which uses
> metaclasses, and it works in Python 2.4 an Python 2.5. See
> http://www.math.bme.hu/~pts/pobjects.py and
> http://www.math.bme.hu/~pts/pobjects_example.py

I have no idea why you want these, and severe trepidation about
dealing with code that uses them "just to be safe."  It smacks of
the over-use I see of doubled underscores.  For @override, just
because you've built a base class for one kind of object does not
mean I have not thought of an interesting way to use 40% of your
code to accomplish my own end.  Why make me cut and paste?  You
are not responsible for the correctness of my flea-brained idea
whether I inherit from your class or not.  For @final, "how dare
you" for similar reasons.  Java at least has an excuse (compilation
can proceed differently).

--Scott David Daniels
Scott.Daniels at Acm.Org

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