On Sat, Dec 14, 2019 at 2:50 AM Stephen J. Turnbull < turnbull.stephen...@u.tsukuba.ac.jp> wrote:
> Did you intend to reply only to me? Nope - I hate list that don’t default to replying to the list (I know that’s an unpopular opinion). I was wondering why no one comment on it. > I’m quite convinced that first() would NOT cause any particular > > confusion, neither for sets nor iterators. > > I don't see how you make that judgment so confidently, since you don't > claim experience with `first`, only the educationally problematic > `next(iter())`. Well, that’s why I said *I’m* convinced, rather than state it as a general truism. I have a lot of experience with newbies, so I think I have a pretty good idea what tends to trip them up. I could be wrong of course, but without actually introducing it using it in and a couple of years worth of teaching, we’ll never know for sure :-) I don't agree. I can't speak for others, but once I understood the > difference between "iterable" and "iterator", "next(iter(iterable))" > was self-explanatory when I first encountered it. Sure — but the newbies I’m talking about don’t yet understand the difference between "iterable" and "iterator", and many people get very far before they do. I *think* the primary target audience for first() would be those folks, so it’s kind of ironic that we’re concerned about confusing them. > I don't see how you > explain all that in terms of first() without the concept of iter(), > and the detail that (iter(iterator)) == iterator. I don’t think you need to — that’s my whole point. In common code, folks rarely work with bare iterators (usually they are implicitly created in a for loop, for instance), so that distinction doesn’t come up. And when it *does* come up, it applies to every use of the iteration protocol: for loops, next, etc. so nothing special about first() I think I made that point already, probably in a note sent to only one person by mistake. Of the top of my head, I can’t think of a single non-contrived example of using a bare iterator in case that is not specifically doing something “special”. Can anyone else? Sure, you can > *tell* students that's how first() works, but how do they apply it in > their own code? You tell them that can use it to get the first item out of a container or other iterable. And you’re done. Some time in the future, they may encounter a bare iterator, and surprised that first() consumes an item. But as I said before, they’ll have other issues as well, and will need to learn about iterators then. -CHB -- Christopher Barker, PhD Python Language Consulting - Teaching - Scientific Software Development - Desktop GUI and Web Development - wxPython, numpy, scipy, Cython
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