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

Answer 3

I just encountered a problem where I didn't have rights to restart my Jupyter instance, and so the post-save hook I wanted couldn't be applied.
So, I extracted the key parts and could run this with python manual_post_save_hook.py:
from io import open
from re import sub
from os.path import splitext
from nbconvert.exporters.script import ScriptExporter
for nb_path in ['notebook1.ipynb', 'notebook2.ipynb']:
base, ext = splitext(nb_path)
script, resources = ScriptExporter().from_filename(nb_path)
# mine happen to all be in Python so I needn't bother with the full flexibility
script_fname = base + '.py'
with open(script_fname, 'w', encoding='utf-8') as f:
# remove 'In [ ]' commented lines peppered about
f.write(sub(r'[\n]{2}# In\[[0-9 ]+\]:\s+[\n]{2}', '\n', script))
You can add your own bells and whistles as you would with the standard post save hook, and the config is the correct way to proceed; sharing this for others who might end up in a similar pinch where they can't get the config edits to go into action.