REF: Implement isin on DTA instead of DTI (#38012)

Author: jbrockmendel

pandas/core/algorithms.py

@@ -433,10 +433,8 @@ def isin(comps: AnyArrayLike, values: AnyArrayLike) -> np.ndarray:
         return cast("Categorical", comps).isin(values)
 
     if needs_i8_conversion(comps):
-        # Dispatch to DatetimeLikeIndexMixin.isin
-        from pandas import Index
-
-        return Index(comps).isin(values)
+        # Dispatch to DatetimeLikeArrayMixin.isin
+        return array(comps).isin(values)
 
     comps, dtype = _ensure_data(comps)
     values, _ = _ensure_data(values, dtype=dtype)

pandas/core/arrays/datetimelike.py

@@ -62,7 +62,7 @@
 from pandas.core.dtypes.missing import is_valid_nat_for_dtype, isna
 
 from pandas.core import nanops, ops
-from pandas.core.algorithms import checked_add_with_arr, unique1d, value_counts
+from pandas.core.algorithms import checked_add_with_arr, isin, unique1d, value_counts
 from pandas.core.arraylike import OpsMixin
 from pandas.core.arrays._mixins import NDArrayBackedExtensionArray
 import pandas.core.common as com
@@ -697,6 +697,59 @@ def map(self, mapper):
 
         return Index(self).map(mapper).array
 
+    def isin(self, values) -> np.ndarray:
+        """
+        Compute boolean array of whether each value is found in the
+        passed set of values.
+
+        Parameters
+        ----------
+        values : set or sequence of values
+
+        Returns
+        -------
+        ndarray[bool]
+        """
+        if not hasattr(values, "dtype"):
+            values = np.asarray(values)
+
+        if values.dtype.kind in ["f", "i", "u", "c"]:
+            # TODO: de-duplicate with equals, validate_comparison_value
+            return np.zeros(self.shape, dtype=bool)
+
+        if not isinstance(values, type(self)):
+            inferrable = [
+                "timedelta",
+                "timedelta64",
+                "datetime",
+                "datetime64",
+                "date",
+                "period",
+            ]
+            if values.dtype == object:
+                inferred = lib.infer_dtype(values, skipna=False)
+                if inferred not in inferrable:
+                    if inferred == "string":
+                        pass
+
+                    elif "mixed" in inferred:
+                        return isin(self.astype(object), values)
+                    else:
+                        return np.zeros(self.shape, dtype=bool)
+
+            try:
+                values = type(self)._from_sequence(values)
+            except ValueError:
+                return isin(self.astype(object), values)
+
+        try:
+            self._check_compatible_with(values)
+        except (TypeError, ValueError):
+            # Includes tzawareness mismatch and IncompatibleFrequencyError
+            return np.zeros(self.shape, dtype=bool)
+
+        return isin(self.asi8, values.asi8)
+
     # ------------------------------------------------------------------
     # Null Handling
 

pandas/core/indexes/base.py

@@ -5145,7 +5145,7 @@ def isin(self, values, level=None):
         """
         if level is not None:
             self._validate_index_level(level)
-        return algos.isin(self, values)
+        return algos.isin(self._values, values)
 
     def _get_string_slice(self, key: str_t):
         # this is for partial string indexing,

pandas/core/indexes/datetimelike.py

@@ -24,7 +24,6 @@
 from pandas.core.dtypes.concat import concat_compat
 from pandas.core.dtypes.generic import ABCIndex, ABCSeries
 
-from pandas.core import algorithms
 from pandas.core.arrays import DatetimeArray, PeriodArray, TimedeltaArray
 from pandas.core.arrays.datetimelike import DatetimeLikeArrayMixin
 import pandas.core.common as com
@@ -500,58 +499,6 @@ def _partial_date_slice(
     __truediv__ = make_wrapped_arith_op("__truediv__")
     __rtruediv__ = make_wrapped_arith_op("__rtruediv__")
 
-    def isin(self, values, level=None):
-        """
-        Compute boolean array of whether each index value is found in the
-        passed set of values.
-
-        Parameters
-        ----------
-        values : set or sequence of values
-
-        Returns
-        -------
-        is_contained : ndarray (boolean dtype)
-        """
-        if level is not None:
-            self._validate_index_level(level)
-
-        if not hasattr(values, "dtype"):
-            values = np.asarray(values)
-
-        if values.dtype.kind in ["f", "i", "u", "c"]:
-            # TODO: de-duplicate with equals, validate_comparison_value
-            return np.zeros(self.shape, dtype=bool)
-
-        if not isinstance(values, type(self)):
-            inferrable = [
-                "timedelta",
-                "timedelta64",
-                "datetime",
-                "datetime64",
-                "date",
-                "period",
-            ]
-            if values.dtype == object:
-                inferred = lib.infer_dtype(values, skipna=False)
-                if inferred not in inferrable:
-                    if "mixed" in inferred:
-                        return self.astype(object).isin(values)
-                    return np.zeros(self.shape, dtype=bool)
-
-            try:
-                values = type(self)(values)
-            except ValueError:
-                return self.astype(object).isin(values)
-
-        try:
-            self._data._check_compatible_with(values)
-        except (TypeError, ValueError):
-            # Includes tzawareness mismatch and IncompatibleFrequencyError
-            return np.zeros(self.shape, dtype=bool)
-
-        return algorithms.isin(self.asi8, values.asi8)
-
     def shift(self, periods=1, freq=None):
         """
         Shift index by desired number of time frequency increments.

pandas/core/indexes/numeric.py

@@ -27,7 +27,6 @@
 from pandas.core.dtypes.generic import ABCSeries
 from pandas.core.dtypes.missing import is_valid_nat_for_dtype, isna
 
-from pandas.core import algorithms
 import pandas.core.common as com
 from pandas.core.indexes.base import Index, maybe_extract_name
 
@@ -434,12 +433,6 @@ def __contains__(self, other: Any) -> bool:
     def is_unique(self) -> bool:
         return super().is_unique and self._nan_idxs.size < 2
 
-    @doc(Index.isin)
-    def isin(self, values, level=None):
-        if level is not None:
-            self._validate_index_level(level)
-        return algorithms.isin(np.array(self), values)
-
     def _can_union_without_object_cast(self, other) -> bool:
         # See GH#26778, further casting may occur in NumericIndex._union
         return is_numeric_dtype(other.dtype)

pandas/core/series.py

@@ -4691,7 +4691,7 @@ def isin(self, values) -> "Series":
         5    False
         Name: animal, dtype: bool
         """
-        result = algorithms.isin(self, values)
+        result = algorithms.isin(self._values, values)
         return self._constructor(result, index=self.index).__finalize__(
             self, method="isin"
         )