On Sun, Oct 16, 2016 at 5:34 AM, Sven R. Kunze <srku...@mail.de> wrote:
> On 16.10.2016 07:08, David Mertz wrote: > >> In case it wasn't entirely clear, I strongly and vehemently opposed this >> unnecessary new syntax. It is confusing, bug prone, and would be difficult >> to teach. > > > "Whom does he teach? Children?" > Me: "What? No, everybody I think. Why?" > She: "It's easy enough to remember what the star does." > As I've said, the folks I teach are mostly working scientists with doctorates in scientific fields and years of programming experience in languages other than Python. For example, rocket scientists at NASA. Now I admit that I don't specifically know how quickly they would pick up on something I've never taught them. But I've written enough teaching materials and articles and books and I have a certain intuition. The way you explained the special case you built up is pretty good, but it's very tailored to making that specific case plausible, and is not general. > She also asked what would the alternative would look like. I wrote: > """ > >>> from itertools import chain > >>> list(chain.from_iterable((i,i,i) for i in range(4))) > [0, 0, 0, 1, 1, 1, 2, 2, 2, 3, 3, 3] > """ > Her reaction was like: "That's supposed to be easy to remember? I find the > star easier." > That is an absolutely terrible construct, obviously. I have to pause and think a while myself to understand what it does. It also answers a very different use case than the one that has been mostly discussed in this thread. A much better spelling is: >>> [i for i in range(4) for _ in range(3)] [0, 0, 0, 1, 1, 1, 2, 2, 2, 3, 3, 3] For some related uses, itertools.repeat() is very useful. But the case that has been discussed far more often is like this: >>> listOfLists = [[1,2,3], [4,5,6,7], [8,9]] >>> flatten(listOfLists) The very long argument is that somehow that would be easier to spell as: >>> [*i for i in listOfLists] It's just not easier. And there are contrary intuitions that will occur to many people based on the several other related-but-different uses of * for packing/unpacking in other contexts. Also, this simplest case might be teachable, but the more general "exactly where can I use that star in a comprehensions" will be far harder to explain plausibly. What's the pattern here? >>> [(*i,) for i in listOfLists] [(1, 2, 3), (4, 5, 6, 7), (8, 9)] >>> [(i,*i) for i in listOfLists] [([1, 2, 3], 1, 2, 3), ([4, 5, 6, 7], 4, 5, 6, 7), ([8, 9], 8, 9)] >>> [(*i,*i) for i in listOfLists] [(1, 2, 3, 1, 2, 3), (4, 5, 6, 7, 4, 5, 6, 7), (8, 9, 8, 9)] >>> [*(i,) for i in listOfLists] # ... no clear intuition here ... >>> [*(*i) for i in listOfLists # ... even more confusing ... Yes! I know those first few are actually doing something different than the proposed new syntax. But explaining that to my rocket scientists or your girlfriend in a consistent and accurate way would be a huge challenge. It would mostly come down to "don't do that, it's too confusing." -- Keeping medicines from the bloodstreams of the sick; food from the bellies of the hungry; books from the hands of the uneducated; technology from the underdeveloped; and putting advocates of freedom in prisons. Intellectual property is to the 21st century what the slave trade was to the 16th.
_______________________________________________ Python-ideas mailing list Pythonfirstname.lastname@example.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/