google/python-fire · error · ValueError

Fire can only be called on .py files.

Error message

Fire can only be called on .py files.

What it means

fire.import_module accepts either an existing path or a dotted module name. If the argument exists on disk but does not end in .py, fire first tries to interpret it as a module name; when that also raises ImportError, it gives up with ValueError('Fire can only be called on .py files.'). It deliberately restricts file-based loading to .py because importlib.util.spec_from_file_location requires .py files.

Source

Thrown at fire/__main__.py:102

  Args:
    module_or_filename (str): string name of path or module.

  Raises:
    ValueError: if the given file is invalid.
    IOError: if the file or module can not be found or imported.

  Returns:
    Tuple[ModuleType, str]: returns the imported module and the module name,
      usually extracted from the path itself.
  """

  if os.path.exists(module_or_filename):
    # importlib.util.spec_from_file_location requires .py
    if not module_or_filename.endswith('.py'):
      try:  # try as module instead
        return import_from_module_name(module_or_filename)
      except ImportError:
        raise ValueError('Fire can only be called on .py files.')

    return import_from_file_path(module_or_filename)

  if os.path.sep in module_or_filename:  # Use / to detect if it was a filename.
    raise OSError('Fire was passed a filename which could not be found.')

  return import_from_module_name(module_or_filename)  # Assume it's a module.


def main(args):
  """Entrypoint for fire when invoked as a module with python -m fire."""

  if len(args) < 2:
    print(cli_string)
    sys.exit(1)

  module_or_filename = args[1]
  module, module_name = import_module(module_or_filename)

View on GitHub (pinned to 716bbc23d7)

Solutions

1. Rename the target so it ends in .py.
2. If the target is a module inside a package, use the dotted module name: `python -m fire mypkg.mymodule`.
3. If the target is not Python at all, invoke fire from within a Python entry point instead of passing the file to python -m fire.

Example fix

// before
python -m fire ./tools/backup serve
// after
python -m fire tools/backup.py serve   # or: python -m fire tools.backup serve

import os
arg = './tools/backup'
if os.path.exists(arg) and not arg.endswith('.py'):
    raise SystemExit('Fire file targets must end in .py; use a dotted module name otherwise')

def is_py_file_target(arg: str) -> bool:
    return os.path.exists(arg) and arg.endswith('.py')

try:
    module, name = fire_import.import_module(arg)
except ValueError as e:
    print(f'{arg}: {e} — rename to .py or pass pkg.mod'); sys.exit(2)

When it happens

Trigger: python -m fire <existing-non-py-path> where the path exists, lacks the .py extension, and is not importable as a dotted module — e.g. `python -m fire ./serve.sh` or a directory-style path to a non-Python file.

Common situations: Passing shell scripts, config files, or extensionless executables to fire; forgetting to rename a Python file that was saved without the .py extension.

Related errors

• Unable to load module from specified path.
• Given file path does not exist.
• Fire was passed a filename which could not be found.
• The command argument must be a string or a sequence of argum
• 2

AI-assisted analysis of google/python-fire@716bbc23d7 (2026-08-28). Data as JSON: /api/errors/dda4a280e168f95c. Report an issue: GitHub.