REF: define _convert_to_indexer in Loc (#31585)

Author: jbrockmendel

pandas/core/indexing.py

@@ -566,7 +566,7 @@ def iat(self) -> "_iAtIndexer":
         return _iAtIndexer("iat", self)
 
 
-class _NDFrameIndexer(_NDFrameIndexerBase):
+class _LocationIndexer(_NDFrameIndexerBase):
     _valid_types: str
     axis = None
 
@@ -1580,10 +1580,6 @@ def _validate_read_indexer(
     def _convert_to_indexer(self, key, axis: int):
         raise AbstractMethodError(self)
 
-
-class _LocationIndexer(_NDFrameIndexer):
-    _takeable: bool = False
-
     def __getitem__(self, key):
         if type(key) is tuple:
             key = tuple(com.apply_if_callable(x, self.obj) for x in key)
@@ -1614,94 +1610,17 @@ def _getbool_axis(self, key, axis: int):
         inds = key.nonzero()[0]
         return self.obj._take_with_is_copy(inds, axis=axis)
 
-    def _convert_to_indexer(self, key, axis: int):
-        """
-        Convert indexing key into something we can use to do actual fancy
-        indexing on a ndarray.
-
-        Examples
-        ix[:5] -> slice(0, 5)
-        ix[[1,2,3]] -> [1,2,3]
-        ix[['foo', 'bar', 'baz']] -> [i, j, k] (indices of foo, bar, baz)
-
-        Going by Zen of Python?
-        'In the face of ambiguity, refuse the temptation to guess.'
-        raise AmbiguousIndexError with integer labels?
-        - No, prefer label-based indexing
-        """
-        labels = self.obj._get_axis(axis)
-
-        if isinstance(key, slice):
-            return self._convert_slice_indexer(key, axis)
-
-        # try to find out correct indexer, if not type correct raise
-        try:
-            key = self._convert_scalar_indexer(key, axis)
-        except TypeError:
-            # but we will allow setting
-            pass
-
-        # see if we are positional in nature
-        is_int_index = labels.is_integer()
-        is_int_positional = is_integer(key) and not is_int_index
-
-        if is_scalar(key) or isinstance(labels, ABCMultiIndex):
-            # Otherwise get_loc will raise InvalidIndexError
-
-            # if we are a label return me
-            try:
-                return labels.get_loc(key)
-            except LookupError:
-                if isinstance(key, tuple) and isinstance(labels, ABCMultiIndex):
-                    if len(key) == labels.nlevels:
-                        return {"key": key}
-                    raise
-            except TypeError:
-                pass
-            except ValueError:
-                if not is_int_positional:
-                    raise
-
-        # a positional
-        if is_int_positional:
-
-            # if we are setting and its not a valid location
-            # its an insert which fails by definition
-
-            # always valid
-            return {"key": key}
-
-        if is_nested_tuple(key, labels):
-            return labels.get_locs(key)
-
-        elif is_list_like_indexer(key):
-
-            if com.is_bool_indexer(key):
-                key = check_bool_indexer(labels, key)
-                (inds,) = key.nonzero()
-                return inds
-            else:
-                # When setting, missing keys are not allowed, even with .loc:
-                return self._get_listlike_indexer(key, axis, raise_missing=True)[1]
-        else:
-            try:
-                return labels.get_loc(key)
-            except LookupError:
-                # allow a not found key only if we are a setter
-                if not is_list_like_indexer(key):
-                    return {"key": key}
-                raise
-
 
 @Appender(IndexingMixin.loc.__doc__)
 class _LocIndexer(_LocationIndexer):
+    _takeable: bool = False
     _valid_types = (
         "labels (MUST BE IN THE INDEX), slices of labels (BOTH "
         "endpoints included! Can be slices of integers if the "
         "index is integers), listlike of labels, boolean"
     )
 
-    @Appender(_NDFrameIndexer._validate_key.__doc__)
+    @Appender(_LocationIndexer._validate_key.__doc__)
     def _validate_key(self, key, axis: int):
 
         # valid for a collection of labels (we check their presence later)
@@ -1867,6 +1786,84 @@ def _get_slice_axis(self, slice_obj: slice, axis: int):
             #  return a DatetimeIndex instead of a slice object.
             return self.obj.take(indexer, axis=axis)
 
+    def _convert_to_indexer(self, key, axis: int):
+        """
+        Convert indexing key into something we can use to do actual fancy
+        indexing on a ndarray.
+
+        Examples
+        ix[:5] -> slice(0, 5)
+        ix[[1,2,3]] -> [1,2,3]
+        ix[['foo', 'bar', 'baz']] -> [i, j, k] (indices of foo, bar, baz)
+
+        Going by Zen of Python?
+        'In the face of ambiguity, refuse the temptation to guess.'
+        raise AmbiguousIndexError with integer labels?
+        - No, prefer label-based indexing
+        """
+        labels = self.obj._get_axis(axis)
+
+        if isinstance(key, slice):
+            return self._convert_slice_indexer(key, axis)
+
+        # try to find out correct indexer, if not type correct raise
+        try:
+            key = self._convert_scalar_indexer(key, axis)
+        except TypeError:
+            # but we will allow setting
+            pass
+
+        # see if we are positional in nature
+        is_int_index = labels.is_integer()
+        is_int_positional = is_integer(key) and not is_int_index
+
+        if is_scalar(key) or isinstance(labels, ABCMultiIndex):
+            # Otherwise get_loc will raise InvalidIndexError
+
+            # if we are a label return me
+            try:
+                return labels.get_loc(key)
+            except LookupError:
+                if isinstance(key, tuple) and isinstance(labels, ABCMultiIndex):
+                    if len(key) == labels.nlevels:
+                        return {"key": key}
+                    raise
+            except TypeError:
+                pass
+            except ValueError:
+                if not is_int_positional:
+                    raise
+
+        # a positional
+        if is_int_positional:
+
+            # if we are setting and its not a valid location
+            # its an insert which fails by definition
+
+            # always valid
+            return {"key": key}
+
+        if is_nested_tuple(key, labels):
+            return labels.get_locs(key)
+
+        elif is_list_like_indexer(key):
+
+            if com.is_bool_indexer(key):
+                key = check_bool_indexer(labels, key)
+                (inds,) = key.nonzero()
+                return inds
+            else:
+                # When setting, missing keys are not allowed, even with .loc:
+                return self._get_listlike_indexer(key, axis, raise_missing=True)[1]
+        else:
+            try:
+                return labels.get_loc(key)
+            except LookupError:
+                # allow a not found key only if we are a setter
+                if not is_list_like_indexer(key):
+                    return {"key": key}
+                raise
+
 
 @Appender(IndexingMixin.iloc.__doc__)
 class _iLocIndexer(_LocationIndexer):