Hi Timothy,

Many thanks for testing this out.

> I just tried to give this a shot.
> First up, I had to remove the ORG-NEWS part of the patch to be able to
> provide it. It would be nice if you could update the patch so this
> applies cleanly.

I'm attaching an updated patch rebased on master.

> I was initially unable to get this to seem to work, until I changed the
> :results type to "output".
>
> #+begin_src python :async :session blah
> return(a)
> #+end_src
>
> #+RESULTS:
> : /tmp/babel-62cQRX/python-EfJ4o4

ob-python session blocks don't use "return", so this should just be:

#+begin_src python :async :session blah
a
#+end_src

#+RESULTS:
: 2

> Finally, I see that this requires :session to be set in order to work.
> Might it be possible to have this work for non-session blocks too? It
> seems odd that what I'd imagine is the harder case (session blocks) is
> supported, but one-shot (non-session) blocks aren't.

The non-session case is substantially different, and I think it would
probably require a separate implementation.

One possible approach would be to modify ob-eval.el, so that
org-babel--shell-command-on-region uses make-process instead of
process-file.

I agree it would be nice to have, but it would take a bit of work to
figure it all out, and there is already ob-async.el [1] that implements
non-session async for all languages. (I wish it could be brought into
org-mode, but it probably can't, because it depends on the external
async.el.)

> p.s. After this is merged, it would be great to see support for other
> languages grow :)

I also have an async implementation for ob-R that's ready after this is
merged :)

Cheers,
Jack

[1] https://github.com/astahlman/ob-async