REF: Remove CategoricalIndex.get_value (#31765)

Author: jbrockmendel

pandas/core/indexes/category.py

@@ -1,4 +1,4 @@
-from typing import TYPE_CHECKING, Any, List
+from typing import Any, List
 import warnings
 
 import numpy as np
@@ -29,9 +29,6 @@
 from pandas.core.indexes.extension import ExtensionIndex, inherit_names
 import pandas.core.missing as missing
 
-if TYPE_CHECKING:
-    from pandas import Series
-
 _index_doc_kwargs = dict(ibase._index_doc_kwargs)
 _index_doc_kwargs.update(dict(target_klass="CategoricalIndex"))
 
@@ -444,35 +441,6 @@ def _maybe_cast_indexer(self, key):
         code = self.codes.dtype.type(code)
         return code
 
-    def get_value(self, series: "Series", key: Any):
-        """
-        Fast lookup of value from 1-dimensional ndarray. Only use this if you
-        know what you're doing
-
-        Parameters
-        ----------
-        series : Series
-            1-dimensional array to take values from
-        key: : scalar
-            The value of this index at the position of the desired value,
-            otherwise the positional index of the desired value
-
-        Returns
-        -------
-        Any
-            The element of the series at the position indicated by the key
-        """
-        k = key
-        try:
-            k = self._convert_scalar_indexer(k, kind="getitem")
-            indexer = self.get_loc(k)
-            return series.take([indexer])[0]
-        except (KeyError, TypeError):
-            pass
-
-        # we might be a positional inexer
-        return Index.get_value(self, series, key)
-
     @Appender(Index.where.__doc__)
     def where(self, cond, other=None):
         # TODO: Investigate an alternative implementation with

pandas/core/series.py

@@ -979,6 +979,9 @@ def _get_value(self, label, takeable: bool = False):
         """
         if takeable:
             return self._values[label]
+
+        # We assume that _convert_scalar_indexer has already been called,
+        #  with kind="loc", if necessary, by the time we get here
         return self.index.get_value(self, label)
 
     def __setitem__(self, key, value):

pandas/tests/series/indexing/test_indexing.py

@@ -564,6 +564,18 @@ def test_categorical_assigning_ops():
     tm.assert_series_equal(s, exp)
 
 
+def test_getitem_categorical_str():
+    # GH#31765
+    ser = pd.Series(range(5), index=pd.Categorical(["a", "b", "c", "a", "b"]))
+    result = ser["a"]
+    expected = ser.iloc[[0, 3]]
+    tm.assert_series_equal(result, expected)
+
+    # Check the intermediate steps work as expected
+    result = ser.index.get_value(ser, "a")
+    tm.assert_series_equal(result, expected)
+
+
 def test_slice(string_series, object_series):
     numSlice = string_series[10:20]
     numSliceEnd = string_series[-10:]