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GH1398 Remove cast from Index(..., dtype='categorical').array #1414

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Merged
merged 6 commits into from
Oct 10, 2025
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GH1398 Remove cast from Index(..., dtype='categorical').array #1414

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GH1398 Remove cast from Index(..., dtype='categorical').array
loicdiridollou Oct 9, 2025
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GH1398 Remove cast from Index(..., dtype='categorical').array
loicdiridollou Oct 9, 2025
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GH1398 Remove cast from Index(..., dtype='categorical').array
loicdiridollou Oct 9, 2025
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GH1398 Remove cast from Index(..., dtype='categorical').array
loicdiridollou Oct 9, 2025
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GH1398 Remove cast from Index(..., dtype='categorical').array
loicdiridollou Oct 9, 2025
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GH1398 PR Feedback
loicdiridollou Oct 9, 2025
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12 changes: 11 additions & 1 deletion pandas-stubs/core/indexes/category.pyi
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Original file line number Diff line number Diff line change
Expand Up @@ -2,10 +2,15 @@ from collections.abc import (
Hashable,
Iterable,
)
from typing import final
from typing import (
final,
type_check_only,
)

import numpy as np
from pandas.core import accessor
from pandas.core.arrays.categorical import Categorical
from pandas.core.base import IndexOpsMixin
from pandas.core.indexes.base import Index
from pandas.core.indexes.extension import ExtensionIndex
from typing_extensions import Self
Expand All @@ -15,9 +20,14 @@ from pandas._typing import (
DtypeArg,
)

@type_check_only
class CategoricalArrayDescriptor:
def __get__(self, instance, owner: type[IndexOpsMixin]) -> Categorical: ...

class CategoricalIndex(ExtensionIndex[S1], accessor.PandasDelegate):
codes: np.ndarray = ...
categories: Index = ...
array = CategoricalArrayDescriptor() # pyrefly: ignore[bad-override]
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There is only one return type, so we can use a static @property instead.

Suggested change
@type_check_only
class CategoricalArrayDescriptor:
def __get__(self, instance, owner: type[IndexOpsMixin]) -> Categorical: ...
class CategoricalIndex(ExtensionIndex[S1], accessor.PandasDelegate):
codes: np.ndarray = ...
categories: Index = ...
array = CategoricalArrayDescriptor() # pyrefly: ignore[bad-override]
class CategoricalIndex(ExtensionIndex[S1], accessor.PandasDelegate):
codes: np.ndarray = ...
categories: Index = ...
@property
def array(self) -> Categorical: ... # pyrefly: ignore[bad-override]

def __new__(
cls,
data: Iterable[S1] = ...,
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5 changes: 1 addition & 4 deletions tests/indexes/test_indexes.py
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Expand Up @@ -1531,10 +1531,7 @@ def test_array_property() -> None:
"""Test that Index.array and semantic Index.array return ExtensionArray and its subclasses"""
# casting due to pandas-dev/pandas-stubs#1383
check(
assert_type(
cast("Index[pd.CategoricalDtype]", Index([1], dtype="category")).array,
pd.Categorical,
),
assert_type(Index([1], dtype="category").array, pd.Categorical),
pd.Categorical,
int,
)
Expand Down