Simon Forman wrote: > Dustan wrote: > >>Can I make enumerate(myObject) act differently? >> >>class A(object): >> def __getitem__(self, item): >> if item > 0: >> return self.sequence[item-1] >> elif item < 0: >> return self.sequence[item] >> elif item == 0: >> raise IndexError, "Index 0 is not valid." >> else: >> raise IndexError, "Invalid Index." >> def __iter__(self): return iter(self.sequence) > > > That final else clause is a little funny... What kind of indices are > you expecting that will be neither less than zero, greater than zero, > or equal to zero? > Good defensive programming albeit of a somewhat extreme nature. Should one of the tests be removed at a later date the else clause will trap occurrences of the no-longer handled case.
> >>Why the funny behavior, you ask? For my class A, it doesn't make sense >>to number everything the standard programming way. Of course, if >>someone uses enumerate, it's going to number the items the same way as >>ever. Is there any way to modify that behavior, any special function to >>set? There doesn't appear to be, according to the docs, but it never >>hurts to make sure. > > > You can write your own enumerate function and then bind that to the > name 'enumerate'. > Yes, but if you do you had better make sure that it gives the standard behavior for normal uses. regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC/Ltd http://www.holdenweb.com Skype: holdenweb http://holdenweb.blogspot.com Recent Ramblings http://del.icio.us/steve.holden -- http://mail.python.org/mailman/listinfo/python-list
