andrew cooke schrieb: >> Just a correction: according to the doc, NotImplemented is not an >> error, but a returned value. > > curious, so it is. i wonder why there is both a special return value > (NotIMplemented) and a related exception (NotImplementedError). seems > very odd to have a value...
They are different and unrelated things. The NotImplentedError is an exception class while NotImplemented is a singleton like None. When a method like __add__ can't handle the other object it returns NotImplemented. It doesn't raise a NotImplementedError. The NotImplemented singleton is an optimization. The interpreter just has to compare the memory address of the returned value with the address of NotImplemented. That's a super fast op in C. Christian -- http://mail.python.org/mailman/listinfo/python-list
