def _save_rest_method(self, method_name, version, method):
    """Store Rest api methods in a list for lookup at call time.

    The list is self._rest_methods, a list of tuples:
      [(<compiled_path>, <path_pattern>, <method_dict>), ...]
    where:
      <compiled_path> is a compiled regex to match against the incoming URL
      <path_pattern> is a string representing the original path pattern,
        checked on insertion to prevent duplicates.     -and-
      <method_dict> is a dict (httpMethod, apiVersion) => (method_name, method)

    This structure is a bit complex, it supports use in two contexts:
      Creation time:
        - SaveRestMethod is called repeatedly, each method will have a path,
          which we want to be compiled for fast lookup at call time
        - We want to prevent duplicate incoming path patterns, so store the
          un-compiled path, not counting on a compiled regex being a stable
          comparison as it is not documented as being stable for this use.
        - Need to store the method that will be mapped at calltime.
        - Different methods may have the same path but different http method.
          and/or API versions.
      Call time:
        - Quickly scan through the list attempting .match(path) on each
          compiled regex to find the path that matches.
        - When a path is matched, look up the API version and method from the
          request and get the method name and method config for the matching
          API method and method name.

    Args:
      method_name: A string containing the name of the API method.
      version: A string containing the version of the API.
      method: A dict containing the method descriptor (as in the api config
        file).
    """
    path_pattern = method.get('path', '') % _API_REST_PATH_FORMAT
    http_method = method.get('httpMethod', '').lower()
    for _, path, methods in self._rest_methods:
      if path == path_pattern:
        methods[(http_method, version)] = method_name, method
        break
    else:
      self._rest_methods.append(
          (self._compile_path_pattern(path_pattern),
           path_pattern,
           {(http_method, version): (method_name, method)}))
dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/tools/devappserver2/endpoints/api_config_manager.py/ApiConfigManager._save_rest_method/swapped operands of `%`