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?

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.

In python3: 'str' does not support the buffer interface

$ python3 editor.py
Traceback (most recent call last):
  File "editor.py", line 9, in <module>
    tf.write(initial_message)
  File "/usr/lib/python3.4/tempfile.py", line 399, in func_wrapper
    return func(*args, **kwargs)
TypeError: 'str' does not support the buffer interface

For python3, use initial_message = b"" to declare the buffered string.

Then use edited_message.decode("utf-8") to decode the buffer into a string.

import sys, tempfile, os
from subprocess import call

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

initial_message = b"" # 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()
    print (edited_message.decode("utf-8"))

Result:

$ python3 editor.py
look a string

Package python-editor:

$ pip install python-editor
$ python
>>> import editor
>>> result = editor.edit(contents="text to put in editor\n")

More details here: https://github.com/fmoo/python-editor

click is a great library for command line processing and it has some utilities, click.edit() is portable and uses the EDITOR environment variable. I typed the line, stuff, into the editor. Notice it is returned as a string. Nice.

(venv) /tmp/editor $ export EDITOR='=mvim -f'
(venv) /tmp/editor $ python
>>> import click
>>> click.edit()
'stuff\n'

Check out the docs https://click.palletsprojects.com/en/7.x/utils/#launching-editors My entire experience:

/tmp $ mkdir editor
/tmp $ cd editor
/tmp/editor $ python3 -m venv venv
/tmp/editor $ source venv/bin/activate
(venv) /tmp/editor $ pip install click
Collecting click
  Using cached https://files.pythonhosted.org/packages/fa/37/45185cb5abbc30d7257104c434fe0b07e5a195a6847506c074527aa599ec/Click-7.0-py2.py3-none-any.whl
Installing collected packages: click
Successfully installed click-7.0
You are using pip version 19.0.3, however version 19.3.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
(venv) /tmp/editor $ export EDITOR='=mvim -f'
(venv) /tmp/editor $ python
Python 3.7.3 (v3.7.3:ef4ec6ed12, Mar 25 2019, 16:52:21)
[Clang 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import click
>>> click.edit()
'stuff\n'
>>>

The PIPE is the problem. VIM is an application that depends on the fact that the stdin/stdout channels are terminals and not files or pipes. Removing the stdin/stdout paramters worked for me.

I would avoid using os.system as it should be replaced by the subprocess module.

The accepted answer does not work for me. edited_message stays the same as initial_message. As explained in the comments, this is caused by vim saving strategy.

There are possible workarounds, but they are not portable to other editors. Instead, I strongly recommend to use click.edit function. With it, your code will look like this:

import click

initial_message = "edit me!"
edited_message = click.edit(initial_message)
print(edited_message)

Click is a third-party library, but you probably should use it anyway if you are writing a console script. click to argparse is the same as requests to urllib.