[nprescott]

I have tried with both python 2.7.18 and python 3.8.6 using Emacs 27.1 and the excerpt works without issue for me; I have no configuration (emacs -Q) beyond pointing org to my virtual environment and allowing python evaluation in org-babel:

  (org-babel-do-load-languages 'org-babel-load-languages '((python . t)))
  (setq org-babel-python-command "~/mpl-venv/bin/python")

Are you perhaps on an outdated version of Emacs?

There have been a few different fixes around the "last line" return value over the years[0][1] but I can't really remember something like your example not working for me personally.

[0]: https://lists.gnu.org/archive/html/emacs-orgmode/2017-11/msg...

[1]: https://orgmode.org/list/[e-mail]/t/#u