Jupyter notebooks - clear output pre-save hook (for cleaner git diffs)

jupyter_notebook_config.py

# This file has to be saved in your Jupyter config directory (found by running
# jupyter --config-dir
# but usually C:\Users\<username>\.jupyter\jupyter_notebook_config.py on Windows

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
        if 'collapsed' in cell['metadata']:
            cell['metadata'].pop('collapsed', 0)

c.FileContentsManager.pre_save_hook = scrub_output_pre_save