It's worth noting that the "buffer()" built-in in Python2 had this behavior, and it enabled a copy-reduction optimization within Twisted's outgoing transport buffer.

There are of course other ways to do this, but it seems like it would be nice to restore this handy optimization; it seems like a bug, or at least an oversight, that the convenience 'bytes+memoryview' (which cannot provide a useful optimization) works, but 'memoryview+bytes' (which would be equally helpful from a convenience perspective _could_ provide a reduction in copying) doesn't.

Despite the bytes.join optimization (which, don't get me wrong, is also very helpful, almost necessary) this remains very useful.