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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_notebook_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):

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 `jupyter 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)
    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.