git pre-commit hook for stripping output from IPython notebooks

nbstripout

#!/usr/bin/env python
"""strip outputs from an IPython Notebook

Opens a notebook, strips its output, and writes the outputless version to the original file.

Useful mainly as a git filter or pre-commit hook for users who don't want to track output in VCS.

This does mostly the same thing as the `Clear All Output` command in the notebook UI.

LICENSE: Public Domain
"""

import io
import sys

try:
    # Jupyter >= 4
    from nbformat import read, write, NO_CONVERT
except ImportError:
    # IPython 3
    try:
        from IPython.nbformat import read, write, NO_CONVERT
    except ImportError:
        # IPython < 3
        from IPython.nbformat import current
    
        def read(f, as_version):
            return current.read(f, 'json')
    
        def write(nb, f):
            return current.write(nb, f, 'json')


def _cells(nb):
    """Yield all cells in an nbformat-insensitive manner"""
    if nb.nbformat < 4:
        for ws in nb.worksheets:
            for cell in ws.cells:
                yield cell
    else:
        for cell in nb.cells:
            yield cell


def strip_output(nb):
    """strip the outputs from a notebook object"""
    nb.metadata.pop('signature', None)
    for cell in _cells(nb):
        if 'outputs' in cell:
            cell['outputs'] = []
        if 'prompt_number' in cell:
            cell['prompt_number'] = None
    return nb


if __name__ == '__main__':
    filename = sys.argv[1]
    with io.open(filename, 'r', encoding='utf8') as f:
        nb = read(f, as_version=NO_CONVERT)
    nb = strip_output(nb)
    with io.open(filename, 'w', encoding='utf8') as f:
        write(nb, f)

pre-commit

#!/bin/sh
#
# strip output of IPython Notebooks
# add this as `.git/hooks/pre-commit`
# to run every time you commit a notebook
#
# requires `nbstripout` to be available on your PATH
#
# LICENSE: Public Domain

if git rev-parse --verify HEAD >/dev/null 2>&1; then
   against=HEAD
else
   # Initial commit: diff against an empty tree object
   against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
fi
 
# Find notebooks to be committed
(
IFS='
'
NBS=`git diff-index -z --cached $against --name-only | grep '.ipynb$' | uniq`

for NB in $NBS ; do
    echo "Removing outputs from $NB"
    nbstripout "$NB"
    git add "$NB"
done
)

exec git diff-index --check --cached $against --

Great snippet, thanks a lot for sharing!

Two suggestions:

1. Small fix: I guess it should be grep '\.ipynb$' with the . escaped, else it will match anything
2. Also add | tr -d '\000' | before grep: NBS=`git diff-index -z --cached $against --name-only | tr -d '\000' | grep '\.ipynb$' | uniq

The second point is because there will be cases where grep considers the input binary (https://unix.stackexchange.com/questions/19907/what-makes-grep-consider-a-file-to-be-binary). This happens to me when using zsh (i.e. getting Binary file (standard input) matches from grep instead of the matchiing parts)