pola-rs/polars · error · ModuleNotFoundError

great_tables is required for `.style`

Error message

great_tables is required for `.style`

What it means

The df.style accessor returns great_tables.GT(self) for spreadsheet-style formatting, and great_tables is an optional dependency. If the import failed (_GREAT_TABLES_AVAILABLE false), accessing the property raises ModuleNotFoundError with a message naming the missing package, since there is no fallback formatter.

Source

Thrown at py-polars/src/polars/dataframe/frame.py:820

        >>> df.style.tab_style(
        ...     style.fill("yellow"),
        ...     loc.body(rows=pl.col("measure_a") == pl.col("measure_a").max()),
        ... )  # doctest: +SKIP

        Put a spanner (high-level label) over measure columns:

        >>> df.style.tab_spanner(
        ...     "Measures", cs.starts_with("measure")
        ... )  # doctest: +SKIP

        Format measure_b values to two decimal places:

        >>> df.style.fmt_number("measure_b", decimals=2)  # doctest: +SKIP
        """
        if not _GREAT_TABLES_AVAILABLE:
            msg = "great_tables is required for `.style`"
            raise ModuleNotFoundError(msg)

        return great_tables.GT(self)

    @property
    def shape(self) -> tuple[int, int]:
        """
        Get the shape of the DataFrame.

        Examples
        --------
        >>> df = pl.DataFrame({"foo": [1, 2, 3, 4, 5]})
        >>> df.shape
        (5, 1)
        """
        return self._df.shape()

    @property
    def height(self) -> int:

View on GitHub (pinned to df599052da)

Solutions

1. pip install great_tables
2. Add it to the project's dependencies/environment lockfile so style-using code runs everywhere
3. Guard with importlib.util.find_spec('great_tables') before styling, and degrade to plain repr/to_html when absent

Example fix

# before
df.style.fmt_number('x', decimals=2)  # ModuleNotFoundError

# after
# pip install great_tables
df.style.fmt_number('x', decimals=2)

import importlib.util

GREAT_TABLES = importlib.util.find_spec('great_tables') is not None
styled = df.style if GREAT_TABLES else df  # skip styling when unavailable

try:
    out = df.style.fmt_number('x', decimals=2)
except ModuleNotFoundError as e:
    if 'great_tables' in str(e):
        out = df  # or render df.to_html() as a plain fallback
    else:
        raise

When it happens

Trigger: Any access of df.style (property access itself raises) in an environment without great_tables installed; partially installed/broken great_tables package; environments provisioned without the 'format' extra.

Common situations: Notebook servers or slim Docker images where only core polars is installed; shared code that styles reports and is run in CI without viz dependencies.

Related errors

• could not get Databricks token: databricks-sdk is not instal
• altair>=5.4.0 is required for `.plot`
• invalid dtype_format value: {fmt!r} (expected format string,
• Required package 'torch' not installed.\nPlease install it u
• altair>=5.4.0 is required for `.plot`

AI-assisted analysis of pola-rs/polars@df599052da (2026-08-16). Data as JSON: /api/errors/d33714228a3654f4. Report an issue: GitHub.