code: def python_script_exists(package=None, module=None):
      
      assert module is not None
      try:
          if package is None:
              path = imp.find_module(module)[1]
          else:
              path = osp.join(imp.find_module(package)[1], module)+'.py'
      except ImportError:
          return
      if not osp.isfile(path):
          path += 'w'
      if osp.isfile(path):
          return path
docs: Return absolute path if Python script exists (otherwise, return None)
      package=None -> module is in sys.path (standard library modules)