in some cases, with a new Emacs, py-shell seems not to receive input, while listed by M-x list-processes RET looks okay and no error elsewhere. Killing the comint-buffer and open that shell again helps AFAICT.
If it’s about receiving results only, executing via non-interactive Python (‘py-fast-process-p’) might be preferable.
From choices offered by ‘py-split-window-on-execute’ no bugs are known with ‘just-two’ –the behaviour of version 6.1.3– and ‘nil’, whilst ‘always’ and ‘t’ have some