I updated to the latest org, and I am not sure if you are seeing a bug. You
might need to fix the space between : and session in your example, and name
the session something. Also, you need to make sure the directory exists.
This example works as expected for me:

#+begin_src python :results output :session t :dir ./run
import os
cwd = os.getcwd()
print("dir: ", cwd)
#+end_src

#+RESULTS:
: dir:  /Users/jkitchin/Box
Sync/kitchingroup/jkitchin/journal/2019/04/05/run

There are still some subtle possible issues, e.g. you cannot change the
:dir after you run this in a session. I am not sure why. Personally I
prefer ipython for sessions.

John

-----------------------------------
Professor John Kitchin
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
@johnkitchin
http://kitchingroup.cheme.cmu.edu



On Wed, Apr 3, 2019 at 1:31 PM Joao Cortes <joaooneillcortes@outlook.pt>
wrote:

> Thanks for checking. Do you know what to do now, assuming It is a bug?
>
>