On Wed, Dec 12, 2018 at 11:31:03AM +1300, Greg Ewing wrote: > Steven D'Aprano wrote: > >I suggest we provide a separate mapview() type that offers only the lazy > >sequence API, without trying to be an iterator at the same time. > > Then we would be back to the bad old days of having two functions > that do almost exactly the same thing.
They aren't "almost exactly the same thing". One is a sequence, which is a rich API that includes random access to items and a length; the other is an iterator, which is an intentionally simple API which fails to meet the needs of some users. > My suggestion was made in > the interests of moving the language in the direction of having > less warts, rather than adding more or moving the existing ones > around. > > I acknowledge that the dual interface is itself a bit wartish, It's a "bit wartish" in the same way that the sun is "a bit warmish". > but it's purely for backwards compatibility And it fails at that too. x = map(str.upper, "abcd") x is iter(x) returns True with the current map, an actual iterator, and False with your hybrid. Current map() is a proper, non-broken iterator; your hybrid is a broken iterator. (That's not me being derogative: its the official term for iterators which don't stay exhausted.) I'd be more charitable if I thought the flaws were mere bugs that could be fixed. But I don't think there is any way to combine two incompatible interfaces, the sequence and iterator APIs, into one object without these sorts of breakages. Take the __next__ method out of your object, and it is a better version of what I proposed earlier. With the __next__ method, its just broken. -- Steve _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
