On Sun, May 26, 2013 at 12:08 AM, PJ Eby <p...@telecommunity.com> wrote: > On Sat, May 25, 2013 at 8:08 AM, Łukasz Langa <luk...@langa.pl> wrote: >> The most important >> change in this version is that I introduced ABC support and completed >> a reference implementation. > > Excellent! A couple of thoughts on the implementation... > > While the dispatch() method allows you to look up what implementation > would be *selected* for a target type, it does not let you figure out > whether a particular method has been *registered* for a type. > > That is, if I have a class MyInt that subclasses int, I can't use > dispatch() to check whether a MyInt implementation has been > registered, because I might get back an implementation registered for > int or object. ISTM there should be some way to get at the raw > registration info, perhaps by exposing a dictproxy for the registry.
I like that idea - types.MappingProxyType makes it straightforward to expose a read-only view of the dispatch registry. > Second, it should be possible to memoize dispatch() using a weak key > dictionary that is cleared if new ABC implementations have been > registered or when a call to register() is made. The way to detect > ABC registrations is via the ABCMeta._abc_invalidation_counter > attribute: if its value is different than the previous value saved > with the cache, the cache must be cleared, and the new value stored. > > (Unfortunately, this is a private attribute at the moment; it might be > a good idea to make it public, however, because it's needed for any > sort of type dispatching mechanism, not just this one particular > generic function implementation.) I think I added an issue on the tracker for that somewhere... yup: http://bugs.python.org/issue16832 Given the global nature of the cache invalidation, it may be better as a module level abc.get_cache_token() function. Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
