(I'm sorry for my delayed response -- I've been travelling and not had reliable Internet access.)
>> Spencer, i would re-think this entire project from the >> beginning. You are trying to make an object out of everything. You >> don't need to make an object of EVERYTHING. > > Very true. I'm not sure I understand. Surely you're not both saying that I shouldn't write a Point class? Here's an expression I'd like very much to be able to type: sphere1.intersect(sphere2).rotated(angle, axis) If I represented points with something already defined, maybe a tuple or a numpy array, then that would risk that the spheres were tangent, that their intersection was not a Circle (a GeometricObject, with a .rotated method), but a point (a tuple, without one). On 2011-12-25, Steven D'Aprano <steve+comp.lang.pyt...@pearwood.info> wrote: > class Line: > intersection_kind = Point > def intersection(self, other): > blah() > return self.intersection_kind(a, b) > > class DrawableLine(Line): > intersection_kind = DrawablePoint If I objected that the intersection of two Lines might, once in a blue moon, be a Line (because they're the same line), this seems like it would edge towards the factory solution that Ian Kelly suggested (i.e. not "return self.intersection_kind(...)", but "return self.factory.create_point(...)" or something similar). Is that so? -Spencer -- http://mail.python.org/mailman/listinfo/python-list
