Your ‘python-shell-interpreter’ doesn’t seem to support readline

Question

I've got this problem with my 25.1 and Python 3.5 on Ubuntu 16.10, but I don't see it being solved anywhere. Wondering what the latest status was. Reproducing:

> emacs -Q --eval '(setq python-shell-interpreter "python3")'

then

M-x run-python gives

Warning (python): Your ‘python-shell-interpreter’ doesn’t seem to support readline, yet ‘python-shell-completion-native’ was t and "python3" is not part of the ‘python-shell-completion-native-disabled-interpreters’ list.  Native completions have been disabled locally.

I saw one idea where an M-x find-function python-shell-completion-native-try would pull up the function from deep (/usr/local/share/emacs/25.1/lisp/progmodes/python.el.gz and the very last line was supposed to be nil "_"))) and not nil ""))). Another conversation here talks about changing inputrc

I switched to another user and I was able to use `run-python' without any warnings. Turns out it was my readline settings. Bash 4.3 added a new readline feature: "set colored-stats on" which I had in .inputrc Removing that line fixed my issue, I think this should be reproducible for all.

Anybody know what the latest is on this? BTW, running Python2 ((setq org-babel-python-command "python2")) doesn't have this problem.

Answer 1

If you don't want to get a 25.2 rc, you can apply the bug fix by adding this to your init.el file:

(with-eval-after-load 'python
  (defun python-shell-completion-native-try ()
    "Return non-nil if can trigger native completion."
    (let ((python-shell-completion-native-enable t)
          (python-shell-completion-native-output-timeout
           python-shell-completion-native-try-output-timeout))
      (python-shell-completion-native-get-completions
       (get-buffer-process (current-buffer))
       nil "_"))))

https://debbugs.gnu.org/cgi/bugreport.cgi?bug=25753#44

Answer 2

I had this disturbing warning in Emacs 25.1 too.

https://debbugs.gnu.org/cgi/bugreport.cgi?bug=24401 has proper solution to enable colored-stats only for Bash:

$ cat ~/.inputrc
$if Bash
set colored-stats on
$endif

Answer 3

A pip install readline did the job for me. Completion within python code blocks is pretty neat to have...

Answer 4

I had this issue in Emacs 27 and Python 3.9, on Debian 11. My workaround was to wrap my ~/.inputrc with $if term=dumb, $else, and $endif. This disables all my psql and python tricks when run inside comint.el (which sets $TERM=dumb), but keeps them when run directly in a regular terminal.