Extracts all the content inside an *.ipynb file and write it to a file of code, non code cells go as comments

extract_ipython_code.py

import os
import sys
import json

languages = dict(
  python=dict(ext='py', comment='#'),
  javascript=dict(ext='js', comment='//')
)

if len(sys.argv) < 2:
  print('Usage {} <ipython notebook> [<ipython notebook>, ...]'.format(sys.argv[0]))
  sys.exit(0)

notebooks = sys.argv[1:]
# print(notebooks)

def extract(notebook, lang_comment):
  lines = []
  for cell in notebook['cells']:
    prepend = ''
    if cell['cell_type'] != 'code':
      # comment non code lines
      prepend = lang_comment + ' '
    lines.extend([(prepend if not s.startswith(lang_comment) else '') + s for s in cell['source']])
    lines.append('\n\n')
  return ''.join(lines)

for notebook in notebooks:
  notebook_path = os.path.abspath(notebook)
  notebook_content = json.load(open(notebook_path, 'r'))
  notebook_language = notebook_content['metadata']['kernelspec'].get('language', 'python')
  if notebook_language not in languages:
    print('Unkown language for notebook: ', notebook_pathk)
  else:
    notebook_name = os.path.splitext(os.path.basename(notebook_path))[0]
    notebook_dirname = os.path.dirname(notebook_path)
    notebook_output_name = notebook_name + '_code.' + languages.get(notebook_language).get('ext')
    notebook_output = os.path.join(notebook_dirname, notebook_output_name)
    lang_comment = languages.get(notebook_language).get('comment')
    extracted = extract(notebook_content, lang_comment)
    with open(notebook_output, 'w') as fout:
      fout.write(extracted)