google/python-fire · error · FireError

Could not consume arg:

Error message

Could not consume arg:

What it means

During traversal, Fire consumes args one at a time by matching them against members (attributes/methods) of the current component. If an argument token cannot be consumed — it matches no accessible member, isn't callable consumable, and isn't a flag — FireError('Could not consume arg:', arg) is raised and recorded in the trace.

Source

Thrown at fire/core.py:649

  Returns:
    component: The component that was found by consuming an arg.
    consumed_args: The args that were consumed by getting this member.
    remaining_args: The remaining args that haven't been consumed yet.
  Raises:
    FireError: If we cannot consume an argument to get a member.
  """
  members = dir(component)
  arg = args[0]
  arg_names = [
      arg,
      arg.replace('-', '_'),  # treat '-' as '_'.
  ]

  for arg_name in arg_names:
    if arg_name in members:
      return getattr(component, arg_name), [arg], args[1:]

  raise FireError('Could not consume arg:', arg)


def _CallAndUpdateTrace(component, args, component_trace, treatment='class',
                        target=None):
  """Call the component by consuming args from args, and update the FireTrace.

  The component could be a class, a routine, or a callable object. This function
  calls the component and adds the appropriate action to component_trace.

  Args:
    component: The component to call
    args: Args for calling the component
    component_trace: FireTrace object that contains action trace
    treatment: Type of treatment used. Indicating whether we treat the component
        as a class, a routine, or a callable.
    target: Target in FireTrace element, default is None. If the value is None,
        the component itself will be used as target.
  Returns:

View on GitHub (pinned to 716bbc23d7)

Solutions

1. Check spelling/case of the argument against the component's members
2. Use `mytool -- --help` to list available members
3. Expose the needed attribute/method as public
4. Pass the value as a flag (--name value) if it was meant as an argument

Example fix

// before
$ mytool statrt  # typo
// after
$ mytool start

args = sys.argv[1:]
missing = [a for a in args if not a.startswith('-') and not hasattr(component, a)]
# note: only meaningful for the first traversal token; prefer --help for full check

try:
    fire.Fire(component)
except fire.core.FireError as e:
    if 'Could not consume arg' in str(e):
        print('Unknown command; see -- --help', file=sys.stderr)
        sys.exit(2)
    raise

When it happens

Trigger: Typo in a subcommand name (mytool stat vs mytool start); passing a positional arg to an object whose members don't include it; accessing a private/mangled attribute that isn't in members; passing a bare value where a method name is expected.

Common situations: Renamed methods after refactoring; case-sensitivity mistakes; trying to access dict-like keys on an object that only supports attribute access.

Related errors

• Given file path does not exist.
• Unable to load module from specified path.
• Fire can only be called on .py files.
• Fire was passed a filename which could not be found.
• The command argument must be a string or a sequence of argum

AI-assisted analysis of google/python-fire@716bbc23d7 (2026-08-28). Data as JSON: /api/errors/9a0a53f4dd91d9b4. Report an issue: GitHub.