pola-rs/polars · error · ModuleNotFoundError

required package '{module_name}' not found. Please install u

Error message

required package '{module_name}' not found.
Please install using the command `pip install {module_root}`.

What it means

ModuleNotFoundError raised by the lazy-import helper when import_module({module_name}) raised ImportError: the optional package required by the calling API is missing from the environment. The message composes an optional err_prefix, the module name, and a pip install hint naming the module root package.

Source

Thrown at py-polars/src/polars/_dependencies.py:298

    ...     err_prefix="super-important package",
    ... )  # doctest: +SKIP
    ImportError: super-important package 'definitely_a_real_module' not installed.
    Please install it using the command `pip install definitely_a_real_module`.
    """
    from polars._utils.various import parse_version
    from polars.exceptions import ModuleUpgradeRequiredError

    module_root = module_name.split(".", 1)[0]
    try:
        module = import_module(module_name)
    except ImportError:
        prefix = f"{err_prefix.strip(' ')} " if err_prefix else ""
        suffix = f" {err_suffix.strip(' ')}" if err_suffix else ""
        err_message = f"{prefix}'{module_name}'{suffix}.\n" + (
            install_message
            or f"Please install using the command `pip install {module_root}`."
        )
        raise ModuleNotFoundError(err_message) from None

    if min_version:
        min_version = parse_version(min_version)
        mod_version = parse_version(module.__version__)
        if mod_version < min_version:
            msg = (
                f"{min_err_prefix} {module_root} "
                f"{'.'.join(str(v) for v in min_version)} or higher"
                f" (found {'.'.join(str(v) for v in mod_version)})"
            )
            raise ModuleUpgradeRequiredError(msg)

    return module


__all__ = [
    # lazy-load rarely-used/heavy builtins (for fast startup)
    "dataclasses",

View on GitHub (pinned to 9b5d73fd00)

Solutions

1. Install the required package with the printed command: pip install <module_root>.

Example fix

pip install <module_root>

When it happens

Trigger: A required third-party package is missing at runtime.

Common situations: See trigger scenarios.

AI-assisted analysis of pola-rs/polars@9b5d73fd00 (2026-08-19). Data as JSON: /api/errors/08be7dd4a0fbfb21. Report an issue: GitHub.