apache/beam · error · ValueError

Path must not be empty.

Error message

Path must not be empty.

What it means

get_code_from_identifier validates that the identifier string is non-empty before splitting on dots. An empty (or falsy) identifier is rejected with ValueError 'Path must not be empty.' This guards upstream callers (_make_function_from_identifier) from passing uninitialized path data.

Source

Thrown at sdks/python/apache_beam/internal/code_object_pickler.py:436

            return obj_
  raise AttributeError(f'Could not find code object with path: {path}')


def get_code_from_identifier(code_object_identifier: str):
  """Returns the code object corresponding to the code object identifier.

  Args:
    code_object_identifier: A string representing the code object identifier.

  Returns:
    The code object.

  Raises:
    ValueError: If the path is empty or invalid.
    AttributeError: If the attribute is not found.
  """
  if not code_object_identifier:
    raise ValueError('Path must not be empty.')
  parts = code_object_identifier.split('.')
  if parts[0] not in sys.modules:
    raise AttributeError(f'Module {parts[0]} not found in sys.modules')
  obj = sys.modules[parts[0]]
  for part in parts[1:]:
    if name_result := _SINGLE_NAME_PATTERN.fullmatch(part):
      obj = _get_code_object_from_single_name_pattern(
          obj, name_result, code_object_identifier)
    elif lambda_with_args_result := _LAMBDA_WITH_ARGS_PATTERN.fullmatch(part):
      obj = _get_code_object_from_lambda_with_args_pattern(
          obj, lambda_with_args_result, code_object_identifier)
    elif lambda_with_hash_result := _LAMBDA_WITH_HASH_PATTERN.fullmatch(part):
      obj = _get_code_object_from_lambda_with_hash_pattern(
          obj, lambda_with_hash_result, code_object_identifier)
    elif default_result := _DEFAULT_PATTERN.fullmatch(part):
      index = int(default_result.group(2))
      if index >= len(obj.__defaults__):
        raise ValueError(

View on GitHub (pinned to 12126d8942)

Solutions

1. Check the identifier is non-empty before calling; fix the code that produced the empty string.
2. Guard with `if identifier:` and skip/fail fast with context about where it came from.
3. Inspect the pickling source that generated the reference to see why the name was blank.

Example fix

// before
fn = _make_function_from_identifier(identifier)  # identifier == ''
// after
if not identifier:
    raise ValueError(f'Cannot unpickle function: empty identifier from {ctx}')
fn = _make_function_from_identifier(identifier)

def ensure_nonempty(path):
    if not path:
        raise ValueError('code object identifier is empty; upstream pickling produced no name')
    return path

def is_valid_identifier(path) -> bool:
    return isinstance(path, str) and bool(path.strip())

try:
    fn = _make_function_from_identifier(ident)
except ValueError as e:
    raise RuntimeError(f'Blank function identifier from serialized reference: {e}') from e

When it happens

Trigger: Calling get_code_from_identifier('') directly, or _make_function_from_identifier receiving an empty/None code-object identifier, typically from an empty attribute name extracted during pickling or a corrupted/blank serialized reference.

Common situations: A pickled payload missing the identifier field; code that builds the path via string concatenation ending up empty; reading function names from metadata that failed to populate.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• cannot check importability of {} instances
• Qual name parts too long
• Invalid pattern for single name: {name_result.group(0)}
• Could not find code object with path: {path}
• Module {parts[0]} not found in sys.modules

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/074b6d8c2cc66b92. Report an issue: GitHub.