CLN: Add allow_slice to is_hashable function

pandas/core/dtypes/inference.py

@@ -376,10 +376,15 @@ def is_named_tuple(obj: object) -> bool:
     return isinstance(obj, abc.Sequence) and hasattr(obj, "_fields")
 
 
-def is_hashable(obj: object) -> TypeGuard[Hashable]:
+def is_hashable(obj: object, allow_slice: bool = True) -> TypeGuard[Hashable]:
     """
     Return True if hash(obj) will succeed, False otherwise.
 
+    If `allow_slice` is False, objects that are slices or tuples containing slices
+    will always return False, even if hash(obj) would succeed.
+    If `allow_slice` is True, slices and tuples containing slices are treated as
+    hashable if hash(obj) does not raise TypeError.
+
     Some types will pass a test against collections.abc.Hashable but fail when
     they are actually hashed with hash().
 
@@ -390,13 +395,17 @@ def is_hashable(obj: object) -> TypeGuard[Hashable]:
     ----------
     obj : object
         The object to check for hashability. Any Python object can be passed here.
+    allow_slice : bool
+        If True, return True if the object is hashable (including slices).
+        If False, return True if the object is hashable and not a slice.
 
     Returns
     -------
     bool
         True if object can be hashed (i.e., does not raise TypeError when
-        passed to hash()), and False otherwise (e.g., if object is mutable
-        like a list or dictionary).
+        passed to hash()) and passes the slice check according to 'allow_slice'.
+        False otherwise (e.g., if object is mutable like a list or dictionary
+        or if allow_slice is False and object is a slice or contains a slice).
 
     See Also
     --------
@@ -422,6 +431,12 @@ def is_hashable(obj: object) -> TypeGuard[Hashable]:
     # Reconsider this decision once this numpy bug is fixed:
     # https://github.com/numpy/numpy/issues/5562
 
+    if allow_slice is False:
+        if isinstance(obj, tuple) and any(isinstance(v, slice) for v in obj):
+            return False
+        elif isinstance(obj, slice):
+            return False
+
     try:
         hash(obj)
     except TypeError:

pandas/core/frame.py

@@ -4050,7 +4050,7 @@ def __getitem__(self, key):
         key = lib.item_from_zerodim(key)
         key = com.apply_if_callable(key, self)
 
-        if is_hashable(key) and not is_iterator(key) and not isinstance(key, slice):
+        if is_hashable(key, allow_slice=False) and not is_iterator(key):
             # is_iterator to exclude generator e.g. test_getitem_listlike
             # As of Python 3.12, slice is hashable which breaks MultiIndex (GH#57500)
 

pandas/core/indexing.py

@@ -793,8 +793,7 @@ def _get_setitem_indexer(self, key):
         if (
             isinstance(ax, MultiIndex)
             and self.name != "iloc"
-            and is_hashable(key)
-            and not isinstance(key, slice)
+            and is_hashable(key, allow_slice=False)
         ):
             with suppress(KeyError, InvalidIndexError):
                 # TypeError e.g. passed a bool
@@ -1147,8 +1146,7 @@ def _contains_slice(x: object) -> bool:
                 # This should never be reached, but let's be explicit about it
                 raise ValueError("Too many indices")  # pragma: no cover
             if all(
-                (is_hashable(x) and not _contains_slice(x)) or com.is_null_slice(x)
-                for x in tup
+                is_hashable(x, allow_slice=False) or com.is_null_slice(x) for x in tup
             ):
                 # GH#10521 Series should reduce MultiIndex dimensions instead of
                 #  DataFrame, IndexingError is not raised when slice(None,None,None)
@@ -1511,12 +1509,8 @@ def _convert_to_indexer(self, key, axis: AxisInt):
 
         # Slices are not valid keys passed in by the user,
         # even though they are hashable in Python 3.12
-        contains_slice = False
-        if isinstance(key, tuple):
-            contains_slice = any(isinstance(v, slice) for v in key)
-
         if is_scalar(key) or (
-            isinstance(labels, MultiIndex) and is_hashable(key) and not contains_slice
+            isinstance(labels, MultiIndex) and is_hashable(key, allow_slice=False)
         ):
             # Otherwise get_loc will raise InvalidIndexError
 

pandas/core/series.py

@@ -953,7 +953,7 @@ def __getitem__(self, key):
         if is_iterator(key):
             key = list(key)
 
-        if is_hashable(key) and not isinstance(key, slice):
+        if is_hashable(key, allow_slice=False):
             # Otherwise index.get_value will raise InvalidIndexError
             try:
                 # For labels that don't resolve as scalars like tuples and frozensets

pandas/tests/dtypes/test_inference.py

@@ -34,6 +34,7 @@
     missing as libmissing,
     ops as libops,
 )
+from pandas.compat import PY312
 from pandas.compat.numpy import np_version_gt2
 from pandas.errors import Pandas4Warning
 
@@ -452,16 +453,55 @@ class UnhashableClass2:
         def __hash__(self):
             raise TypeError("Not hashable")
 
+    class HashableSlice:
+        def __init__(self, start, stop, step=None):
+            self.slice = slice(start, stop, step)
+
+        def __eq__(self, other):
+            return isinstance(other, HashableSlice) and self.slice == other.slice
+
+        def __hash__(self):
+            return hash((self.slice.start, self.slice.stop, self.slice.step))
+
+        def __repr__(self):
+            return (
+                f"HashableSlice({self.slice.start}, {self.slice.stop}, "
+                f"{self.slice.step})"
+            )
+
     hashable = (1, 3.14, np.float64(3.14), "a", (), (1,), HashableClass())
     not_hashable = ([], UnhashableClass1())
     abc_hashable_not_really_hashable = (([],), UnhashableClass2())
+    hashable_slice = HashableSlice(1, 2)
+    tuple_with_slice = (slice(1, 2), 3)
 
     for i in hashable:
         assert inference.is_hashable(i)
+        assert inference.is_hashable(i, allow_slice=True)
+        assert inference.is_hashable(i, allow_slice=False)
     for i in not_hashable:
         assert not inference.is_hashable(i)
+        assert not inference.is_hashable(i, allow_slice=True)
+        assert not inference.is_hashable(i, allow_slice=False)
     for i in abc_hashable_not_really_hashable:
         assert not inference.is_hashable(i)
+        assert not inference.is_hashable(i, allow_slice=True)
+        assert not inference.is_hashable(i, allow_slice=False)
+
+    assert inference.is_hashable(hashable_slice)
+    assert inference.is_hashable(hashable_slice, allow_slice=True)
+    assert inference.is_hashable(hashable_slice, allow_slice=False)
+
+    if PY312:
+        for obj in [slice(1, 2), tuple_with_slice]:
+            assert inference.is_hashable(obj)
+            assert inference.is_hashable(obj, allow_slice=True)
+            assert not inference.is_hashable(obj, allow_slice=False)
+    else:
+        for obj in [slice(1, 2), tuple_with_slice]:
+            assert not inference.is_hashable(obj)
+            assert not inference.is_hashable(obj, allow_slice=True)
+            assert not inference.is_hashable(obj, allow_slice=False)
 
     # numpy.array is no longer collections.abc.Hashable as of
     # https://github.com/numpy/numpy/pull/5326, just test