REF: fix calls to Index.get_value (#31112)

Author: jbrockmendel

pandas/core/indexes/base.py

@@ -4621,34 +4621,31 @@ def argsort(self, *args, **kwargs) -> np.ndarray:
     @Appender(_index_shared_docs["get_value"] % _index_doc_kwargs)
     def get_value(self, series, key):
 
+        if not is_scalar(key):
+            # if key is not a scalar, directly raise an error (the code below
+            # would convert to numpy arrays and raise later any way) - GH29926
+            raise InvalidIndexError(key)
+
         # if we have something that is Index-like, then
         # use this, e.g. DatetimeIndex
         # Things like `Series._get_value` (via .at) pass the EA directly here.
         s = extract_array(series, extract_numpy=True)
         if isinstance(s, ExtensionArray):
-            if is_scalar(key):
-                # GH 20882, 21257
-                # First try to convert the key to a location
-                # If that fails, raise a KeyError if an integer
-                # index, otherwise, see if key is an integer, and
-                # try that
-                try:
-                    iloc = self.get_loc(key)
-                    return s[iloc]
-                except KeyError:
-                    if len(self) > 0 and (self.holds_integer() or self.is_boolean()):
-                        raise
-                    elif is_integer(key):
-                        return s[key]
-            else:
-                # if key is not a scalar, directly raise an error (the code below
-                # would convert to numpy arrays and raise later any way) - GH29926
-                raise InvalidIndexError(key)
-
-        s = com.values_from_object(series)
-        k = com.values_from_object(key)
+            # GH 20882, 21257
+            # First try to convert the key to a location
+            # If that fails, raise a KeyError if an integer
+            # index, otherwise, see if key is an integer, and
+            # try that
+            try:
+                iloc = self.get_loc(key)
+                return s[iloc]
+            except KeyError:
+                if len(self) > 0 and (self.holds_integer() or self.is_boolean()):
+                    raise
+                elif is_integer(key):
+                    return s[key]
 
-        k = self._convert_scalar_indexer(k, kind="getitem")
+        k = self._convert_scalar_indexer(key, kind="getitem")
         try:
             return self._engine.get_value(s, k, tz=getattr(series.dtype, "tz", None))
         except KeyError as e1:

pandas/core/indexes/category.py

@@ -503,8 +503,8 @@ def get_value(self, series: AnyArrayLike, key: Any):
         Any
             The element of the series at the position indicated by the key
         """
+        k = key
         try:
-            k = com.values_from_object(key)
             k = self._convert_scalar_indexer(k, kind="getitem")
             indexer = self.get_loc(k)
             return series.take([indexer])[0]

pandas/core/indexes/numeric.py

@@ -1,3 +1,5 @@
+from typing import TYPE_CHECKING
+
 import numpy as np
 
 from pandas._libs import index as libindex, lib
@@ -38,6 +40,9 @@
 )
 from pandas.core.ops import get_op_result_name
 
+if TYPE_CHECKING:
+    from pandas import Series
+
 _num_index_shared_docs = dict()
 
 
@@ -438,17 +443,18 @@ def _format_native_types(
         )
         return formatter.get_result_as_array()
 
-    def get_value(self, series, key):
+    def get_value(self, series: "Series", key):
         """
         We always want to get an index value, never a value.
         """
         if not is_scalar(key):
             raise InvalidIndexError
 
-        k = com.values_from_object(key)
-        loc = self.get_loc(k)
-        new_values = com.values_from_object(series)[loc]
+        loc = self.get_loc(key)
+        if not is_scalar(loc):
+            return series.iloc[loc]
 
+        new_values = series._values[loc]
         return new_values
 
     def equals(self, other) -> bool:

pandas/core/series.py

@@ -808,6 +808,10 @@ def _slice(self, slobj: slice, axis: int = 0, kind=None) -> "Series":
 
     def __getitem__(self, key):
         key = com.apply_if_callable(key, self)
+
+        if key is Ellipsis:
+            return self
+
         try:
             result = self.index.get_value(self, key)
 
@@ -830,8 +834,6 @@ def __getitem__(self, key):
             if isinstance(key, tuple) and isinstance(self.index, MultiIndex):
                 # kludge
                 pass
-            elif key is Ellipsis:
-                return self
             elif com.is_bool_indexer(key):
                 pass
             else:
@@ -939,7 +941,7 @@ def _get_value(self, label, takeable: bool = False):
         """
         if takeable:
             return com.maybe_box_datetimelike(self._values[label])
-        return self.index.get_value(self._values, label)
+        return self.index.get_value(self, label)
 
     def __setitem__(self, key, value):
         key = com.apply_if_callable(key, self)