TYP: Fix return type of Series.keys() fro list to Index (#1101) (#1106)

* Update series.pyi, tackling issue #1101

Imported Index from pandas
and
Changed keys method:
def keys(self) -> Index: ...

* Update test_series.py

Add a test for issue # 1101

* Update tests/test_series.py

Following the pandas pattern.

Co-authored-by: Irv Lustig <[email protected]>

* Fix import issue in series.pyi to resolve Ruff error

* Delete test

---------

Co-authored-by: Irv Lustig <[email protected]>

Author: janlodewijk

pandas-stubs/core/series.pyi

@@ -30,6 +30,7 @@ from matplotlib.axes import (
 )
 import numpy as np
 from pandas import (
+    Index,
     Period,
     PeriodDtype,
     Timedelta,
@@ -58,7 +59,6 @@ from pandas.core.indexes.accessors import (
     TimedeltaProperties,
     TimestampProperties,
 )
-from pandas.core.indexes.base import Index
 from pandas.core.indexes.category import CategoricalIndex
 from pandas.core.indexes.datetimes import DatetimeIndex
 from pandas.core.indexes.interval import IntervalIndex
@@ -653,7 +653,7 @@ class Series(IndexOpsMixin[S1], NDFrame):
     ) -> _str: ...
     def to_xarray(self) -> xr.DataArray: ...
     def items(self) -> Iterable[tuple[Hashable, S1]]: ...
-    def keys(self) -> list: ...
+    def keys(self) -> Index: ...
     @overload
     def to_dict(self, *, into: type[dict] = ...) -> dict[Any, S1]: ...
     @overload

tests/test_series.py

@@ -3546,6 +3546,12 @@ def test_series_dict() -> None:
     )
 
 
+def test_series_keys_type() -> None:
+    # GH 1101
+    s = pd.Series([1, 2, 3])
+    check(assert_type(s.keys(), pd.Index), pd.Index)
+
+
 def test_series_int_float() -> None:
     # pyright infers mixtures of int and float in a list as list[int | float]
     check(assert_type(pd.Series([1, 2, 3]), "pd.Series[int]"), pd.Series, np.integer)