fix_nb.py

import nbformat
import functools
import sys


def get_key(obj, key):
    if isinstance(obj, dict):
        return obj.get(key, None)
    elif isinstance(obj, (list, tuple)) and key < len(obj):
        return obj[key]
    else:
        return None


def dig(obj, *keys):
    return functools.reduce(get_key, keys, obj)


def is_png(c):
    if c['source'] != '':
        return False
    return dig(c, 'outputs', 0, 'data', 'image/png')


file = sys.argv[1]
nb = nbformat.read(file, 4)
for c in filter(is_png, nb.cells):
    c['metadata']['editable'] = False
    c['metadata']['jupyter'] = {}
    c['metadata']['jupyter']['source_hidden'] = True
nbformat.write(nb, open(file, 'wt'))