On Mon, Jun 18, 2018 at 4:12 AM, Chris Angelico <ros...@gmail.com> wrote: > On Mon, Jun 18, 2018 at 10:50 AM, Steven D'Aprano <st...@pearwood.info> wrote:
>>>> items[-0:] # failed parallel > ['spam', 'ham', 'foo', 'bar', 'quux'] > > So you use -1 in slices to parallel 1 (unlike using ~1 as with > indexing), and everything works *except zero*. Which means that the > slice-assignment form of insert is easy to write, but the > slice-assignment form of append isn't. > > Mikhail, if it were possible to append using slice assignment, would > that meet the case? > How? like this: items[-0:] = [item] One of main motivation is actually to have just 'item' on the right side. So your idea is to have special syntax for 'last item' so as to avoid something like: c = len(L) L[c:c] = [...] But IIUC you're still about _iterable_ on the right-hand part? > However, this would be far from the first time > that a much-hated-on proposal leads to one that has actual support, > perhaps by restricting it, or maybe by generalizing it, or something. I think it is currently quite restricted. So imo it's rather generalizing that could make change. Namely the idea for 'L[] = item' seems plausible for append() method only, and for the types that have this method. Python array type has similar method set as lists. Numpy arrays have also append() and insert() methods, but they do not change arrays in-place. So just for keeping it more or less focused - assume we're considering the 'L[] = item' approach, say for mutable types. So one syntax generalization possible is towards insert() method. Although IMO it could be made into nice syntax only by introducing some symbol into the index notation. For example: L[] = item append(item) L[^] = item ? appendleft(item) L[^0] = item insert (0, item) ... L[^i] = item insert(i, x) Note, I am not responsible for the adequacy of the technical part - since it may be not plausible technically. So just speculating here: if that was added, then could it be linked to corresponding methods? For example for collections.deque type: deq[] = item deq.append(item) deq[^] = item deq.appendleft(item) ... deq[^i] = item deq.insert(i, item) So syntactically - I would say it makes more or less complete picture. Because insert() and append() come hand in hand semantically. And with operator-only variant or without special symbol - it seems it is not possible, (at least not with bareable index notation). _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
