Brandt Bucher <brandtbuc...@gmail.com> added the comment:
I apologize - I should have been clearer about what this accomplishes. I'll use list addition as an example, but this works for any binary operation on these containers. If the left operand has a refcount of exactly one, it will simply mutate in-place rather than making an unnecessary copy. The simplest example of this is with literals: [0] + list1 This just modifies the literal [0] in-place rather than creating an unnecessary copy. However, the more common use case is adding named lists. Currently, when adding list1 + list2 + list3, two copies (with one reference each) are made: - The intermediate result of list1 + list2. - The sum of this intermediate result and list3. Only the second of these is actually returned - the first is used once and thrown away. The effect of this patch is to only create *at most one* (instead of n-1) copy for any arbitrarily long list summation, as this intermediate result will just mutate in-place for lists 3-n. ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue36229> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
