ipython notebook --script deprecated. How to replace with post save hook?

Question

I have been using "ipython --script" to automatically save a .py file for each ipython notebook so I can use it to import classes into other notebooks. But this recenty stopped working, and I get the following error message:

`--script` is deprecated. You can trigger nbconvert via pre- or post-save hooks:
ContentsManager.pre_save_hook
FileContentsManager.post_save_hook
A post-save hook has been registered that calls:
ipython nbconvert --to script [notebook]
which behaves similarly to `--script`.

As I understand this I need to set up a post-save hook, but I do not understand how to do this. Can someone explain?

Answer 1

[UPDATED per comment by @mobius dumpling]

Find your config files:

Jupyter / ipython >= 4.0

jupyter --config-dir

ipython <4.0

ipython locate profile default

If you need a new config:

Jupyter / ipython >= 4.0

jupyter notebook --generate-config

ipython <4.0

ipython profile create

Within this directory, there will be a file called [jupyter | ipython]_notebook_config.py, put the following code from ipython's GitHub issues page in that file:

import os
from subprocess import check_call

c = get_config()

def post_save(model, os_path, contents_manager):
    """post-save hook for converting notebooks to .py scripts"""
    if model['type'] != 'notebook':
        return # only do this for notebooks
    d, fname = os.path.split(os_path)
    check_call(['ipython', 'nbconvert', '--to', 'script', fname], cwd=d)

c.FileContentsManager.post_save_hook = post_save

For Jupyter, replace ipython with jupyter in check_call.

Note that there's a corresponding 'pre-save' hook, and also that you can call any subprocess or run any arbitrary code there...if you want to do any thing fancy like checking some condition first, notifying API consumers, or adding a git commit for the saved script.

Cheers,

-t.

Answer 2

Here is another approach that doesn't invoke a new thread (with check_call). Add the following to jupyter_notebook_config.py as in Tristan's answer:

import io
import os
from notebook.utils import to_api_path

_script_exporter = None

def script_post_save(model, os_path, contents_manager, **kwargs):
    """convert notebooks to Python script after save with nbconvert

    replaces `ipython notebook --script`
    """
    from nbconvert.exporters.script import ScriptExporter

    if model['type'] != 'notebook':
        return

    global _script_exporter
    if _script_exporter is None:
        _script_exporter = ScriptExporter(parent=contents_manager)
    log = contents_manager.log

    base, ext = os.path.splitext(os_path)
    py_fname = base + '.py'
    script, resources = _script_exporter.from_filename(os_path)
    script_fname = base + resources.get('output_extension', '.txt')
    log.info("Saving script /%s", to_api_path(script_fname, contents_manager.root_dir))
    with io.open(script_fname, 'w', encoding='utf-8') as f:
        f.write(script)

c.FileContentsManager.post_save_hook = script_post_save

Disclaimer: I'm pretty sure I got this from SO somwhere, but can't find it now. Putting it here so it's easier to find in future (: