pandas-dev/pandas · error · NotImplementedError

does not support reshape as backed by a 1D…

Error message

{type(self)} does not support reshape as backed by a 1D pyarrow.ChunkedArray.

What it means

ArrowExtensionArray is backed by a 1D pyarrow.ChunkedArray, so the numpy-style reshape (which can change dimensionality) is structurally impossible. The reshape method is therefore unconditionally overridden to raise NotImplementedError. This is a hard API contract, not a runtime state.

Solutions

1. Convert to numpy first with .to_numpy().reshape(...) or np.asarray(arr).reshape(...), then wrap back if needed.
2. If 2D data is required, build a DataFrame or use a numpy-backed array (dtype='int64') instead of the pyarrow dtype.
3. Avoid calling reshape directly on ArrowExtensionArray instances.

Example fix

// before
arr = pd.array([1, 2, 3, 4], dtype="int64[pyarrow]")
arr.reshape(2, 2)
// after
arr = pd.array([1, 2, 3, 4], dtype="int64[pyarrow]")
np.asarray(arr).reshape(2, 2)

def safe_reshape(arr, shape):
    import numpy as np
    if hasattr(arr, "_pa_array"):  # ArrowExtensionArray
        return np.asarray(arr).reshape(shape)
    return arr.reshape(shape)

from pandas.core.arrays.arrow import ArrowExtensionArray

def is_arrow_backed(arr) -> bool:
    return isinstance(arr, ArrowExtensionArray)

try:
    arr.reshape(shape)
except NotImplementedError:
    np.asarray(arr).reshape(shape)

When it happens

Trigger: Calling .reshape(...) on a Series or ExtensionArray backed by an ArrowDtype (e.g. pd.array([1,2,3], dtype='int64[pyarrow]').reshape(3,1)) or any code path that delegates to ExtensionArray.reshape.

Common situations: Migrating numpy/ndarray code to pyarrow-backed pandas arrays; libraries (e.g. sklearn) that call reshape on inputs; reshaping a single Series for matrix operations.

Related errors

• Converting strings to
• groupby first/last only supports 1D ExtensionArrays
• interpolate is not implemented for dtype=
• {pa_type}
• Unsupported type ' ' for ArrowExtensionArray

AI-assisted analysis of pandas-dev/pandas@3b7651241d (2026-08-11). Data as JSON: /api/errors/9a55bba848377260. Report an issue: GitHub.

Appendix: source

Thrown at pandas/core/arrays/arrow/array.py:1921

            indices = np.array([], dtype=np.intp)
            uniques = self._from_pyarrow_array(
                pa.chunked_array([], type=encoded.type.value_type)
            )
        else:
            # GH 54844
            combined = encoded.combine_chunks()
            pa_indices = combined.indices
            if pa_indices.null_count > 0:
                pa_indices = _safe_fill_null(pa_indices, -1)
            indices = pa_indices.to_numpy(zero_copy_only=False, writable=True).astype(
                np.intp, copy=False
            )
            uniques = self._from_pyarrow_array(combined.dictionary)

        return indices, uniques

    def reshape(self, *args, **kwargs):
        raise NotImplementedError(
            f"{type(self)} does not support reshape "
            f"as backed by a 1D pyarrow.ChunkedArray."
        )

    def round(self, decimals: int = 0, *args, **kwargs) -> Self:
        """
        Round each value in the array a to the given number of decimals.

        Parameters
        ----------
        decimals : int, default 0
            Number of decimal places to round to. If decimals is negative,
            it specifies the number of positions to the left of the decimal point.
        *args, **kwargs
            Additional arguments and keywords have no effect.

        Returns
        -------

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