DEPR: Index.asi8 (#37877)

Author: jbrockmendel

doc/source/whatsnew/v1.2.0.rst

@@ -474,7 +474,8 @@ Deprecations
 - :class:`Index` methods ``&``, ``|``, and ``^`` behaving as the set operations :meth:`Index.intersection`, :meth:`Index.union`, and :meth:`Index.symmetric_difference`, respectively, are deprecated and in the future will behave as pointwise boolean operations matching :class:`Series` behavior.  Use the named set methods instead (:issue:`36758`)
 - :meth:`Categorical.is_dtype_equal` and :meth:`CategoricalIndex.is_dtype_equal` are deprecated, will be removed in a future version (:issue:`37545`)
 - :meth:`Series.slice_shift` and :meth:`DataFrame.slice_shift` are deprecated, use :meth:`Series.shift` or :meth:`DataFrame.shift` instead (:issue:`37601`)
-- Partial slicing on unordered :class:`DatetimeIndexes` with keys, which are not in Index is deprecated and will be removed in a future version (:issue:`18531`)
+- Partial slicing on unordered :class:`DatetimeIndex` with keys, which are not in Index is deprecated and will be removed in a future version (:issue:`18531`)
+- Deprecated :meth:`Index.asi8` for :class:`Index` subclasses other than :class:`DatetimeIndex`, :class:`TimedeltaIndex`, and :class:`PeriodIndex` (:issue:`37877`)
 - The ``inplace`` parameter of :meth:`Categorical.remove_unused_categories` is deprecated and will be removed in a future version (:issue:`37643`)
 
 .. ---------------------------------------------------------------------------

pandas/core/indexes/base.py

@@ -415,6 +415,11 @@ def asi8(self):
         ndarray
             An ndarray with int64 dtype.
         """
+        warnings.warn(
+            "Index.asi8 is deprecated and will be removed in a future version",
+            FutureWarning,
+            stacklevel=2,
+        )
         return None
 
     @classmethod
@@ -4738,12 +4743,13 @@ def argsort(self, *args, **kwargs) -> np.ndarray:
         >>> idx[order]
         Index(['a', 'b', 'c', 'd'], dtype='object')
         """
-        result = self.asi8
-
-        if result is None:
-            result = np.array(self)
+        if needs_i8_conversion(self.dtype):
+            # TODO: these do not match the underlying EA argsort methods GH#37863
+            return self.asi8.argsort(*args, **kwargs)
 
-        return result.argsort(*args, **kwargs)
+        # This works for either ndarray or EA, is overriden
+        #  by RangeIndex, MultIIndex
+        return self._data.argsort(*args, **kwargs)
 
     @final
     def get_value(self, series: "Series", key):

pandas/core/indexes/numeric.py

@@ -1,5 +1,6 @@
 import operator
 from typing import Any
+import warnings
 
 import numpy as np
 
@@ -266,6 +267,11 @@ def inferred_type(self) -> str:
     @property
     def asi8(self) -> np.ndarray:
         # do not cache or you'll create a memory leak
+        warnings.warn(
+            "Index.asi8 is deprecated and will be removed in a future version",
+            FutureWarning,
+            stacklevel=2,
+        )
         return self._values.view(self._default_dtype)
 
 

pandas/core/tools/numeric.py

@@ -10,6 +10,7 @@
     is_number,
     is_numeric_dtype,
     is_scalar,
+    needs_i8_conversion,
 )
 from pandas.core.dtypes.generic import ABCIndexClass, ABCSeries
 
@@ -123,8 +124,9 @@ def to_numeric(arg, errors="raise", downcast=None):
         values = arg.values
     elif isinstance(arg, ABCIndexClass):
         is_index = True
-        values = arg.asi8
-        if values is None:
+        if needs_i8_conversion(arg.dtype):
+            values = arg.asi8
+        else:
             values = arg.values
     elif isinstance(arg, (list, tuple)):
         values = np.array(arg, dtype="O")

pandas/core/window/rolling.py

@@ -337,6 +337,13 @@ def _get_roll_func(self, func_name: str) -> Callable[..., Any]:
             )
         return window_func
 
+    @property
+    def _index_array(self):
+        # TODO: why do we get here with e.g. MultiIndex?
+        if needs_i8_conversion(self._on.dtype):
+            return self._on.asi8
+        return None
+
     def _get_window_indexer(self) -> BaseIndexer:
         """
         Return an indexer class that will compute the window start and end bounds
@@ -345,7 +352,7 @@ def _get_window_indexer(self) -> BaseIndexer:
             return self.window
         if self.is_freq_type:
             return VariableWindowIndexer(
-                index_array=self._on.asi8, window_size=self.window
+                index_array=self._index_array, window_size=self.window
             )
         return FixedWindowIndexer(window_size=self.window)
 
@@ -2140,7 +2147,7 @@ def _get_window_indexer(self) -> GroupbyIndexer:
         """
         rolling_indexer: Type[BaseIndexer]
         indexer_kwargs: Optional[Dict[str, Any]] = None
-        index_array = self._on.asi8
+        index_array = self._index_array
         window = self.window
         if isinstance(self.window, BaseIndexer):
             rolling_indexer = type(self.window)

pandas/tests/indexes/test_common.py

@@ -13,7 +13,16 @@
 from pandas.core.dtypes.common import is_period_dtype, needs_i8_conversion
 
 import pandas as pd
-from pandas import CategoricalIndex, MultiIndex, RangeIndex
+from pandas import (
+    CategoricalIndex,
+    DatetimeIndex,
+    Int64Index,
+    MultiIndex,
+    PeriodIndex,
+    RangeIndex,
+    TimedeltaIndex,
+    UInt64Index,
+)
 import pandas._testing as tm
 
 
@@ -348,6 +357,18 @@ def test_ravel_deprecation(self, index):
         with tm.assert_produces_warning(FutureWarning):
             index.ravel()
 
+    def test_asi8_deprecation(self, index):
+        # GH#37877
+        if isinstance(
+            index, (Int64Index, UInt64Index, DatetimeIndex, TimedeltaIndex, PeriodIndex)
+        ):
+            warn = None
+        else:
+            warn = FutureWarning
+
+        with tm.assert_produces_warning(warn):
+            index.asi8
+
 
 @pytest.mark.parametrize("na_position", [None, "middle"])
 def test_sort_values_invalid_na_position(index_with_missing, na_position):