Re: asynchronous python code blocks in org-mode

[Tom <tmbdev@gmail.com>]

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On Mon, Nov 30, 2015 at 1:06 PM, John Kitchin <jkitchin@andrew.cmu.edu>
wrote:

> I have not thought about sessions and asynchronous execution. It would
> mean a queue and a different way to pass code to the process, which I
> have not thought through yet. What to do when there are dependencies for
> example,...
>

A good way of converting synchronous into asynchronous code is to use
futures/promises. Usually, that's done via data structures, but within
Emacs buffers, it could be done via text strings.

How might that work? org-babel-execute:python could wait for, say, 0.1 sec
for an immediate result. If the computation doesn't finish within that
time, it returns a "future", a magic string like
"org_mode_future_result(1234) ###MAGIC###". This would then get inserted as
output into the org-mode buffer. Later, when the actual result becomes
available from the subprocess, that invokes a callback on the org-python
mode buffer and replaces tihs magic string with the actual result, and
dequeues and executes the next command if necessary.

(Picking a Python-parseable expression would even allow futures to be used
in some other Python computations as if it were an actual value.)

I think that would allow much of the current API to remain in place.
Obviously, some things simply can't work. For example,
org-babel-reassemble-table expects an actual result, not a future; such
post-processing would have to move to a hook function, which probably would
be cleaner anyway.

Tom

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