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DOC: clarify pandas.unique return type #65638

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mroeschke merged 1 commit into from
May 16, 2026
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DOC: clarify pandas.unique return type #65638

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23 changes: 14 additions & 9 deletions pandas/core/algorithms.py
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Original file line number Diff line number Diff line change
Expand Up @@ -342,15 +342,20 @@ def unique(values):

Returns
-------
numpy.ndarray, ExtensionArray or NumpyExtensionArray

The return can be:

* Index : when the input is an Index
* Categorical : when the input is a Categorical dtype
* ndarray : when the input is a Series/ndarray

Return numpy.ndarray, ExtensionArray or NumpyExtensionArray.
Index, ExtensionArray or numpy.ndarray
The return type depends on the type of the input:

* :class:`Index` : when the input is an :class:`Index`, the result is
an :class:`Index` (or a subclass such as :class:`DatetimeIndex`).
* :class:`ExtensionArray` : when the input has an
:class:`ExtensionDtype` (for example :class:`Categorical`,
tz-aware ``datetime64``, :class:`IntervalArray`, a masked
integer/boolean/float array, an Arrow-backed array, or
:class:`NumpyExtensionArray`), the result is an
:class:`ExtensionArray` of the same dtype.
* :class:`numpy.ndarray` : for any other input (a NumPy-dtype
:class:`Series`, a :class:`numpy.ndarray`, or any other 1-D
array-like), the result is a :class:`numpy.ndarray`.

See Also
--------
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