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

Scott David Daniels Scott.Daniels at Acm.Org
Mon Mar 30 00:03:03 CEST 2009

Steven D'Aprano wrote:
> ... Perhaps I just haven't worked on enough 20,000 line projects, but I 
> don't get the point of @override. It doesn't prevent somebody from 
> writing (deliberately or accidentally) B.F in the absence of A.F, since 
> the coder can simply leave off the @override.
? B.F vs. A.F?  Could you expand this a trifle?

> If @override is just a way of catching spelling mistakes, perhaps it 
> would be better in pylint or pychecker. What have I missed?

If, for example, you have a huge testing framework, and some developers
are given the task of developing elements from the framework by (say)
overriding the test_sources and test_outcome methods, They can be
handed an example module with @override demonstrating where to make
the changes.

     class TestMondoDrive(DriveTestBase):

         def test_sources(self):
             return os.listdir('/standard/mondo/tests')

         def test_outcome(self, testname, outcome):
             if outcome != 'success':
                 self.failures('At %s %s failed: %s' % (
                     time.strftime('%Y.%m.%d %H:%M:%S'),
                     test_name, outcome))
                 assert False, "I've no idea how to deal with success"

The resulting tests will be a bit easier to read, because you can
easily distinguish between support methods and framework methods.
Further, the entire warp drive test is not started if we stupidly
spell the second "test_result" (as it was on the Enterprise tests).

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

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