On Mon, Nov 28, 2016 at 1:32 PM, Chris Barker <chris.bar...@noaa.gov> wrote:
> On Mon, Nov 28, 2016 at 10:22 AM, Guido van Rossum <gu...@python.org> > wrote: > > >> At calling time, the subclass' method will be found, and used, and the >>> search stops there -- no way to know if there is one with the same name >>> further up the MRO. >>> >>> This is simply incompatable with a language this dynamic. >>> >> >> Not so fast! Python is also so dynamic that you can easily create a >> metaclass (or a class decorator) that does the checking (assuming >> reasonable behavior of all classes involved) at class definition time. >> > > but that's class definition time -- can't classes be dynamically mangled > later on -- after subclasses have been defined? > They can, and they @override can be bypassed. I don't see that as a condemnation of @overload -- it just means that it's not perfect, which is fine with me (given that we're talking about monkey-patching here). > If I have this right the mro is set at class definition time, so it is > knows which classes are in the tree -- but class objects themselves are > mutable -- methods can be added later on. so a subclass could have a > method that isn't overriding anything when it's defined, but ends up > overriding something later on, 'cause the base class changed under it. > > Isn't this why the mro is searched at method calling time? rather than a > static table being used? (if not -- wouldnt that be a nice optimization?) > > Granted -- this kind of late class mangling has got to be pretty unusual > (and maybe only useful for mocking, or??) but it is there. > > Which is why it could be useful to have some syntax or convention for > specifying "I'm intending to override a method", that linters or type > checkers, or whatever external tool, can use. But it can't be enforced at > runtime in the language. > Depends on how much enforcement you need. Bike locks also don't typically enforce that your bike doesn't get stolen... -- --Guido van Rossum (python.org/~guido)
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