Question

I want to call up an editor in a python script to solicit input from the user, much like crontab e or git commit does.

Here’s a snippet from what I have running so far. (In the future, I might use $EDITOR instead of vim so that folks can customize to their liking.)

tmp_file = '/tmp/up.'+''.join(random.choice(string.ascii_uppercase + string.digits) for x in range(6))
edit_call = [ "vim",tmp_file]
edit = subprocess.Popen(edit_call,stdin=subprocess.PIPE, stdout=subprocess.PIPE, shell=True )   

My problem is that by using Popen, it seems to keep my i/o with the python script from going into the running copy of vim, and I can’t find a way to just pass the i/o through to vim. I get the following error.

Vim: Warning: Output is not to a terminal
Vim: Warning: Input is not from a terminal

What’s the best way to call a CLI program from python, hand control over to it, and then pass it back once you’re finished with it?

Answer 1

Calling up $EDITOR is easy. I’ve written this kind of code to call up editor:

import sys, tempfile, os
from subprocess import call

EDITOR = os.environ.get('EDITOR', 'vim')  # that easy!

initial_message = ''  # if you want to set up the file somehow

with tempfile.NamedTemporaryFile(suffix=".tmp") as tf:
  tf.write(initial_message)
  tf.flush()
  call([EDITOR, tf.name])

  # do the parsing with `tf` using regular File operations.
  # for instance:
  tf.seek(0)
  edited_message = tf.read()

The good thing here is the libraries handle creating and removing the temporary file.