pandas-dev/pandas · error · NotImplementedError

not implemented for

Error message

{op.__name__} not implemented for {type(other)}

What it means

Raised by ArrowExtensionArray._cmp_method when the `other` operand of a comparison is neither array-like (ExtensionArray/ndarray/list/range) nor a recognized scalar. This is the terminal else-branch: pandas does not know how to broadcast a comparison against an arbitrary object, so it raises NotImplementedError naming the operand's type.

Solutions

1. Convert the operand to a scalar or array-like first: list(other), np.asarray(other), or wrap in a Series.
2. If it is a pyarrow Scalar, call .as_py() to get a native Python scalar before comparing.
3. Implement __eq__/__lt__ on your custom type returning a comparable scalar.
4. Avoid comparing against containers like dict/set that have no elementwise semantics.

Example fix

# before
import pyarrow as pa
arr = pd.array([1, 2, 3], dtype="int64[pyarrow]")
arr == pa.scalar(2)  # pa.Scalar is not 'is_scalar' -> NotImplementedError

# after
arr == pa.scalar(2).as_py()

import pyarrow as pa
from pandas.api.types import is_scalar, is_list_like

def normalize_operand(other):
    if isinstance(other, pa.Scalar):
        return other.as_py()
    if is_list_like(other) and not isinstance(other, (list, range)):
        return list(other)
    return other

import pyarrow as pa
from pandas.api.types import is_scalar

def is_cmp_operand(other) -> bool:
    if isinstance(other, pa.Scalar):
        return False  # must call .as_py() first
    return is_scalar(other) or hasattr(other, 'dtype') or isinstance(other, (list, range))

When it happens

Trigger: Comparing an ArrowExtensionArray against a custom Python object, a dict, a tuple, a set, or a pyarrow Scalar that escaped the is_scalar check; arr == some_object where some_object.__eq__ does not cooperate.

Common situations: User-defined types passed as comparison operands; passing a row from a DataFrame (a Series) works, but a raw dict/tuple does not; comparing against a pa.Scalar directly.

Related errors

• Can only string multiply by an integer.
• DateOffset is intra-day and cannot be applied to…
• Invalid value ' ' for dtype
• __invert__ is not supported for string dtypes
• operation ' ' not supported for dtype ' ' with

AI-assisted analysis of pandas-dev/pandas@3b7651241d (2026-08-11). Data as JSON: /api/errors/860d001829f037da. Report an issue: GitHub.

Appendix: source

Thrown at pandas/core/arrays/arrow/array.py:1152

                # GH#62157 match non-pyarrow behavior
                result = ops.invalid_comparison(self, other, op)
                result = pa.array(result, type=pa.bool_())
            else:
                try:
                    result = pc_func(self._pa_array, self._box_pa(other))
                except (pa.lib.ArrowNotImplementedError, pa.lib.ArrowInvalid):
                    mask = isna(self) | isna(other)
                    valid = ~mask
                    result = np.zeros(len(self), dtype="bool")
                    np_array = np.array(self)
                    try:
                        result[valid] = op(np_array[valid], other)
                    except TypeError:
                        result = ops.invalid_comparison(self, other, op)
                    result = pa.array(result, type=pa.bool_())
                    result = pc.if_else(valid, result, None)
        else:
            raise NotImplementedError(
                f"{op.__name__} not implemented for {type(other)}"
            )
        return ArrowExtensionArray(result)

    def _op_method_error_message(self, other, op) -> str:
        if hasattr(other, "dtype"):
            other_type = f"dtype '{other.dtype}'"
        else:
            other_type = f"object of type {type(other)}"
        return (
            f"operation '{op.__name__}' not supported for "
            f"dtype '{self.dtype}' with {other_type}"
        )

    def _evaluate_op_method(self, other, op, arrow_funcs) -> Self:
        if (
            is_list_like(other)
            and not isinstance(other, (np.ndarray, ExtensionArray, list))

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