On Fri, Sep 24, 2010 at 2:18 AM, Tarek Ziadé firstname.lastname@example.org wrote:
I think it goes further than documentation at this point. ABC is present and used in the stdlib, not the doc. So asking a class about its capabilities is a feature we provide for third-party code.
Minor nit - we can only ask a fairly limited subset of questions along these lines (i.e. does *this* class/instance implement *this* ABC?). More interesting questions like "which ABCs does this class/instance explicitly implement?" are currently impossible (see http://bugs.python.org/issue5405).
Back on topic - I like Guido's approach. While we can debate the merits of LBYL signature checking forever without reaching agreement (for the record, my opinion is that static checks should be thought of as a bunch of implicit unit tests that you get "for free"), providing a way to explicitly request ABC signature checks in the abc module probably isn't a bad idea. If nothing else, invoking that check can become a recommended part of the unit test suite for classes that claim to implement ABCs. Is getting the method signatures right *sufficient* for ABC compliance? No. Is it *necessary*? Yes. It's the latter point that makes this feature potentially worth standardising.