On Thu, Jun 6, 2019 at 9:48 AM Chris Angelico <ros...@gmail.com> wrote: > They have a difference for the built-in list type in that slicing a > list returns a new list with references to the same objects, thus "x = > x[:]" is going to give you an equivalent but distinct list. That's an > important point in some contexts, but it's by no means "completely > different".
Alright Chris, I would rephrase it like this: they are different because one of them represent the original list (when at the left hand side), and the other represent a new list (when at the right hand side). Whether or not they are "completely different" is a subjective matter and I will not enforce it. For me, they are really different. I think the trick it used here is: let's sacrifice a little bit of low-level consistency, as normally nobody would use list slicing (which always means a copy on right hand side) on the left hand side, so let's redefine it to mean in-place modification. And descriptor and left hand slicing is probably the only two exceptions where an assignment (=) can actually change things in place (you see, this is really an exceptional case for =). And it will become more confusing if L[:] := thing is used, it is now an expression which kind of let you think about "right hand side" (e.g. what about z = (L[:] := [7,8,9,10])). L[:] := thing currently does not work in python3.8a3, throws a "Syntax Error: cannot use named assignment with subscript". Python-Ideas mailing list -- python-dev(a)python.org To unsubscribe send an email to python-ideas-leave(a)python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/
