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File save hooks
===============
You can configure functions that are run whenever a file is saved. There are
two hooks available:
* ``ContentsManager.pre_save_hook`` runs on the API path and model with
content. This can be used for things like stripping output that people don't
like adding to VCS noise.
* ``FileContentsManager.post_save_hook`` runs on the filesystem path and model
without content. This could be used to commit changes after every save, for
instance.
They are both called with keyword arguments::
pre_save_hook(model=model, path=path, contents_manager=cm)
post_save_hook(model=model, os_path=os_path, contents_manager=cm)
Examples
--------
These can both be added to :file:`jupyter_server_config.py`.
A pre-save hook for stripping output::
def scrub_output_pre_save(model, **kwargs):
"""scrub output before saving notebooks"""
# only run on notebooks
if model['type'] != 'notebook':
return
# only run on nbformat v4
if model['content']['nbformat'] != 4:
return
for cell in model['content']['cells']:
if cell['cell_type'] != 'code':
continue
cell['outputs'] = []
cell['execution_count'] = None
c.FileContentsManager.pre_save_hook = scrub_output_pre_save
A post-save hook to make a script equivalent whenever the notebook is saved
(replacing the ``--script`` option in older versions of the notebook):
.. code-block:: python
import io
import os
from jupyter_server.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
This could be a simple call to ``jupyter nbconvert --to script``, but spawning
the subprocess every time is quite slow.
.. note::
Assigning a new hook to e.g. ``c.FileContentsManager.pre_save_hook`` will override any existing one.
If you want to add new hooks and keep existing ones, you should use e.g.:
.. code-block:: python
contents_manager.register_pre_save_hook(script_pre_save)
contents_manager.register_post_save_hook(script_post_save)
Hooks will then be called in the order they were registered.
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