Kyle Meyer writes: > That's on a Debian system with the python executable pointing to Python > 2.7.16. If I set org-babel-python-command to python3 (3.7.3) at the top > of test-ob-python.el, I see the same thing. I haven't dug any farther > yet. Jack, presumably you don't see the stall on your end? No, the tests don't stall on my end (Archlinux with manually compiled emacs 28). I also tested on a debian10vm and the tests passed there too. But since we know it's related to 4df12ea39 that gives some clues...could you try the attached patch to see if it fixes things? Also, could you try executing some simple ob-python session blocks and see if they hang? e.g., #+begin_src python :session :results output print(1+1) #+end_src #+begin_src python :session :results value 1+1 #+end_src