pandas-dev/pandas · error · TypeError

operation '{name}' not supported for dtype '{self.dtype}'

Error message

operation '{name}' not supported for dtype '{self.dtype}'

What it means

StringArray._accumulate supports cumsum, cummin, cummax but explicitly forbids cumprod, raising TypeError. A cumulative product of strings is undefined, so the operation is rejected up front rather than producing garbage.

Source

Thrown at pandas/core/arrays/string_.py:1010

            - cumsum
            - cumprod
        skipna : bool, default True
            If True, skip NA values.
        **kwargs
            Additional keyword arguments passed to the accumulation function.
            Currently, there is no supported kwarg.

        Returns
        -------
        array

        Raises
        ------
        NotImplementedError : subclass does not define accumulations
        """
        if name == "cumprod":
            msg = f"operation '{name}' not supported for dtype '{self.dtype}'"
            raise TypeError(msg)

        # We may need to strip out trailing NA values
        tail: np.ndarray | None = None
        na_mask: np.ndarray | None = None
        ndarray = self._ndarray
        np_func = {
            "cumsum": np.cumsum,
            "cummin": np.minimum.accumulate,
            "cummax": np.maximum.accumulate,
        }[name]

        if self._hasna:
            na_mask = cast("npt.NDArray[np.bool_]", isna(ndarray))
            if np.all(na_mask):
                return type(self)(ndarray, dtype=self.dtype)
            if skipna:
                if name == "cumsum":
                    ndarray = np.where(na_mask, "", ndarray)

View on GitHub (pinned to 71959b8cb9)

Solutions

1. Do not call cumprod on string data.
2. Convert numeric strings first: s.astype(float).cumprod().
3. Exclude string columns from cumprod via select_dtypes.

Example fix

// before
string_series.cumprod()

// after
string_series.astype(float).cumprod()

if name == 'cumprod':
    raise TypeError('cumprod is not supported for string dtype')

def is_supported_accumulation(name: str) -> bool:
    return name in {'cumsum', 'cummin', 'cummax'}

When it happens

Trigger: Calling string_series.cumprod(), or df.cumprod() on a DataFrame that includes a string column, or any accumulation pipeline that runs cumprod across all columns.

Common situations: Generic df.cumprod() calls; accumulation utilities applied uniformly; mistakenly treating string-encoded numbers as numeric without conversion.

Related errors

• Cannot change data-type for string array.
• Invalid value '{value}' for dtype '{self.dtype}'. Value shou
• Invalid value for dtype 'str'. Value should be a string or m
• Cannot perform reduction '{name}' with string dtype
• {func_name} requires a Series, Index, ExtensionArray, np.nda

AI-assisted analysis of pandas-dev/pandas@71959b8cb9 (2026-08-07). Data as JSON: /api/errors/cc1d8790f122443a. Report an issue: GitHub.