PERF: improve iloc list indexing

pandas/core/indexing.py

@@ -1697,34 +1697,38 @@ def _get_slice_axis(self, slice_obj, axis=0):
         else:
             return self.obj.take(slice_obj, axis=axis, convert=False)
 
-    def _get_list_axis(self, key_list, axis=0):
+    def _get_list_axis(self, key, axis=0):
         """
-        Return Series values by list or array of integers
+        Return Series values by array of integers
 
         Parameters
         ----------
-        key_list : list-like positional indexer
+        key : list-like positional indexer (already converted to array)
         axis : int (can only be zero)
 
         Returns
         -------
         Series object
         """
-
-        # validate list bounds
-        self._is_valid_list_like(key_list, axis)
-
-        # force an actual list
-        key_list = list(key_list)
-        return self.obj.take(key_list, axis=axis, convert=False)
+        try:
+            return self.obj.take(key, axis=axis, convert=False)
+        except IndexError:
+            # re-raise with different error message
+            raise IndexError("positional indexers are out-of-bounds")
 
     def _getitem_axis(self, key, axis=0):
 
         if isinstance(key, slice):
             self._has_valid_type(key, axis)
             return self._get_slice_axis(key, axis=axis)
 
-        elif is_bool_indexer(key):
+        if isinstance(key, list):
+            try:
+                key = np.asarray(key)
+            except TypeError:  # pragma: no cover
+                pass
+
+        if is_bool_indexer(key):
             self._has_valid_type(key, axis)
             return self._getbool_axis(key, axis=axis)
 
@@ -1734,6 +1738,7 @@ def _getitem_axis(self, key, axis=0):
 
         # a single integer
         else:
+
             key = self._convert_scalar_indexer(key, axis)
 
             if not is_integer(key):

pandas/core/series.py

@@ -2378,7 +2378,8 @@ def take(self, indices, axis=0, convert=True, is_copy=False, **kwargs):
         --------
         numpy.ndarray.take
         """
-        nv.validate_take(tuple(), kwargs)
+        if kwargs:
+            nv.validate_take(tuple(), kwargs)
 
         # check/convert indicies here
         if convert:
@@ -2388,7 +2389,7 @@ def take(self, indices, axis=0, convert=True, is_copy=False, **kwargs):
         new_index = self.index.take(indices)
         new_values = self._values.take(indices)
         return self._constructor(new_values,
-                                 index=new_index).__finalize__(self)
+                                 index=new_index, fastpath=True).__finalize__(self)
 
     def isin(self, values):
         """

pandas/indexes/base.py

@@ -1668,7 +1668,8 @@ def _append_same_dtype(self, to_concat, name):
     @Appender(_index_shared_docs['take'] % _index_doc_kwargs)
     def take(self, indices, axis=0, allow_fill=True,
              fill_value=None, **kwargs):
-        nv.validate_take(tuple(), kwargs)
+        if kwargs:
+            nv.validate_take(tuple(), kwargs)
         indices = _ensure_platform_int(indices)
         if self._can_hold_na:
             taken = self._assert_take_fillable(self.values, indices,