allow loc setitem to accept a slice

Author: Dr-Irv

pandas-stubs/core/frame.pyi

@@ -220,7 +220,9 @@ class _LocIndexerFrame(_LocIndexer):
     @overload
     def __setitem__(
         self,
-        idx: MaskType | StrLike | _IndexSliceTuple | list[ScalarT] | IndexingInt,
+        idx: (
+            MaskType | StrLike | _IndexSliceTuple | list[ScalarT] | IndexingInt | slice
+        ),
         value: Scalar | NAType | NaTType | ArrayLike | Series | DataFrame | list | None,
     ) -> None: ...
     @overload

pandas-stubs/core/series.pyi

@@ -208,7 +208,7 @@ class _LocIndexerSeries(_LocIndexer, Generic[S1]):
     @overload
     def __setitem__(
         self,
-        idx: Index | MaskType,
+        idx: Index | MaskType | slice,
         value: S1 | ArrayLike | Series[S1] | None,
     ) -> None: ...
     @overload

tests/test_frame.py

@@ -7,7 +7,6 @@
     Iterator,
     Mapping,
     MutableMapping,
-    Sequence,
 )
 import csv
 import datetime
@@ -39,7 +38,6 @@
 from pandas.core.series import Series
 import pytest
 from typing_extensions import (
-    Never,
     TypeAlias,
     assert_never,
     assert_type,
@@ -3763,22 +3761,9 @@ def test_info() -> None:
     check(assert_type(df.info(show_counts=None), None), type(None))
 
 
-def test_series_typed_dict() -> None:
-    """Test that no error is raised when constructing a series from a typed dict."""
+def test_frame_single_slice() -> None:
+    # GH 572
+    df = pd.DataFrame([1, 2, 3])
+    check(assert_type(df.loc[:], pd.DataFrame), pd.DataFrame)
 
-    class MyDict(TypedDict):
-        a: str
-        b: str
-
-    my_dict = MyDict(a="", b="")
-    sr = pd.Series(my_dict)
-    check(assert_type(sr, pd.Series), pd.Series)
-
-
-def test_series_empty_dtype() -> None:
-    """Test for the creation of a Series from an empty list GH571 to map to a Series[Any]."""
-    new_tab: Sequence[Never] = []  # need to be typehinted to please mypy
-    check(assert_type(pd.Series(new_tab), "pd.Series[Any]"), pd.Series)
-    check(assert_type(pd.Series([]), "pd.Series[Any]"), pd.Series)
-    # ensure that an empty string does not get matched to Sequence[Never]
-    check(assert_type(pd.Series(""), "pd.Series[str]"), pd.Series)
+    df.loc[:] = 1 + df

tests/test_series.py

@@ -16,6 +16,7 @@
     Any,
     Generic,
     Literal,
+    TypedDict,
     TypeVar,
     Union,
     cast,
@@ -33,6 +34,7 @@
 from pandas.core.window import ExponentialMovingWindow
 import pytest
 from typing_extensions import (
+    Never,
     Self,
     TypeAlias,
     assert_never,
@@ -3465,3 +3467,32 @@ def test_apply_dateoffset() -> None:
         pd.Series,
         pd.DateOffset,
     )
+
+
+def test_series_single_slice() -> None:
+    # GH 572
+    s = pd.Series([1, 2, 3])
+    check(assert_type(s.loc[:], "pd.Series[int]"), pd.Series, np.integer)
+
+    s.loc[:] = 1 + s
+
+
+def test_series_typed_dict() -> None:
+    """Test that no error is raised when constructing a series from a typed dict."""
+
+    class MyDict(TypedDict):
+        a: str
+        b: str
+
+    my_dict = MyDict(a="", b="")
+    sr = pd.Series(my_dict)
+    check(assert_type(sr, pd.Series), pd.Series)
+
+
+def test_series_empty_dtype() -> None:
+    """Test for the creation of a Series from an empty list GH571 to map to a Series[Any]."""
+    new_tab: Sequence[Never] = []  # need to be typehinted to please mypy
+    check(assert_type(pd.Series(new_tab), "pd.Series[Any]"), pd.Series)
+    check(assert_type(pd.Series([]), "pd.Series[Any]"), pd.Series)
+    # ensure that an empty string does not get matched to Sequence[Never]
+    check(assert_type(pd.Series(""), "pd.Series[str]"), pd.Series)