Make python executable in `ob-ipython--create-driver` a configurable parameter

[millejoh]

At the moment ob-ipython will look for the first python it finds in PATH, but this won't work too well if a user has multiple python environments (like conda).

One thought - use Python Shell Exec Path as the default, but allow the user to specify a custom value.

[hhalex]

I totally agree, on my system I want to use Python 3, but with IPython on Emacs, I want to use Python 2.7

Anyway, there is a variable called python-shell-interpreter that holds the chosen python version inside emacs: the version that should be used instead. Therefore, in the code

(defun ob-ipython--create-driver ()
  (when (not (ignore-errors (process-live-p (ob-ipython--get-driver-process))))
    (ob-ipython--create-process "ob-ipython-driver"
                                (list (locate-file (if (eq system-type 'windows-nt) "python.exe" "python")
                                                   exec-path)
                                      ob-ipython-driver-path
                                      (number-to-string ob-ipython-driver-port)))
    ;; give driver a chance to bind to a port and start serving
    ;; requests. so horrible; so effective.
    (sleep-for 1)))

we should read python-shell-interpreter

(if (eq system-type 'windows-nt) "python.exe" python-shell-interpreter)

instead of "python"

(if (eq system-type 'windows-nt) "python.exe" "python")

Changing that fixed my issue with ob-ipython (It was using Python 3 instead of Python 2.7 to run the driver, and the module "jupyter_client" was not found).

[gregsexton]

Yep, customizing this makes a lot of sense. I went with the python-shell-interpreter suggestion. Just pushed now. Let me know if this doesn't solve your problem. Thanks to you both.