Like dict.update, but recursive.

recursive_dict_update.py

def _recursive_dict_update(x, y):
  for key, val in y.iteritems():
    if isinstance(val, dict):
      if not x.has_key(key):
        x[key] = {}
      x[key] = _recursive_dict_update(x[key], val)
    elif isinstance(val, list):
      if not x.has_key(key):
        x[key] = []
      x[key].extend(val)
    else:
      x[key] = val
  return x