That is not a new idea. So far I have always rejected it because I worry about both false positives and false negatives. Trying to enforce that the method *behaves* as it should (or even its return type) is hopeless; there can be a variety of reasons to modify the argument list while still conforming to (the intent of) the interface. I also worry that it will slow everything down. That said, if you want to provide a standard mechanism that can *optionally* be turned on to check argument conformance, e.g. by using a class or method decorator on the subclass, I would be fine with that (as long as it runs purely at class-definition time; it shouldn't slow down class instantiation or method calls). It will probably even find some bugs. It will also surely have to be tuned to avoid certain classes false positives. --Guido On Thu, Sep 23, 2010 at 7:37 AM, Tarek Ziadé <ziade.tarek@gmail.com> wrote:
Hello,
ABC __subclasshook__ implementations will only check that the method is present in the class. That's the case for example in collections.Container. It will check that the __contains__ method is present but that's it. It won't check that the method has only one argument. e.g. __contains__(self, x)
The problem is that the implemented method could have a different list of arguments and will eventually fail.
Using inspect, we could check in __subclasshook__ that the arguments defined are the same than the ones defined in the abstractmethod.-- the name and the ordering.
I can even think of a small function in ABC for that: same_signature(method1, method2) => True or False
Regards Tarek
-- Tarek Ziadé | http://ziade.org _______________________________________________ Python-ideas mailing list Python-ideas@python.org http://mail.python.org/mailman/listinfo/python-ideas
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