Jared Grubb wrote:
On 25 Jun 2009, at 17:41, Steven D'Aprano wrote:
What you really want is a fast way of initialising a list, given another list. That was your use-case, after all. Swapping the contents is just one particular implementation of that fast-initialise.
FWIW, this use case really sounds a lot like rvalue references, a new feature being added to the new C++0x standard. The basic idea is that, for efficiency reasons, you want to be able to "sink" the contents an object and leave the object in a destructable (but not necessarily valid) state.
This would be a tough (and probably inappropriate?) feature in Python, but I mention it because the concept might provide further context/justifications/trade-offs/ideas for what is being discussed here.
The OP might consider code that does the swap if the refcount is 1, otherwise does something akin to recur(arg.copy()) (which _will_ have a refcount of 0). --Scott David Daniels Scott.Daniels@Acm.Org