[cc to py-dev again] Guido van Rossum wrote: > On 2/17/06, Thomas Heller <[EMAIL PROTECTED]> wrote: >> Guido van Rossum wrote: >>> So here's a new proposal. >>> >>> Let's add a generic missing-key handling method to the dict class, as >>> well as a default_factory slot initialized to None. The implementation >>> is like this (but in C): >>> >>> def on_missing(self, key): >>> if self.default_factory is not None: >>> value = self.default_factory() >>> self[key] = value >>> return value >>> raise KeyError(key) >>> >>> When __getitem__() (and *only* __getitem__()) finds that the requested >>> key is not present in the dict, it calls self.on_missing(key) and >>> returns whatever it returns -- or raises whatever it raises. >>> __getitem__() doesn't need to raise KeyError any more, that's done by >>> on_missing(). >> Will this also work when PyDict_GetItem() does not find the key? > > Ouch, tricky. It should, of course, but the code will be a tad tricky > because it's not supposed to inc the refcount. Thanks for reminding > me! >
Ahem, I'm still looking for ways to 'overtake' the dict to implement weird and fancy things. Can on_missing be overridden in subclasses (writing the subclass in C would not be a problem)? Thanks, Thomas _______________________________________________ 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
