CLN: de-duplicate _isnan (#37373)

Author: jbrockmendel

pandas/core/indexes/category.py

@@ -377,11 +377,6 @@ def astype(self, dtype, copy=True):
 
         return Index.astype(self, dtype=dtype, copy=copy)
 
-    @cache_readonly
-    def _isnan(self):
-        """ return if each value is nan"""
-        return self._data.codes == -1
-
     @doc(Index.fillna)
     def fillna(self, value, downcast=None):
         value = self._validate_scalar(value)

pandas/core/indexes/datetimelike.py

@@ -78,7 +78,7 @@ def wrapper(left, right):
 
 
 @inherit_names(
-    ["inferred_freq", "_isnan", "_resolution_obj", "resolution"],
+    ["inferred_freq", "_resolution_obj", "resolution"],
     DatetimeLikeArrayMixin,
     cache=True,
 )

pandas/core/indexes/extension.py

@@ -277,3 +277,7 @@ def astype(self, dtype, copy=True):
         # pass copy=False because any copying will be done in the
         #  _data.astype call above
         return Index(new_values, dtype=new_values.dtype, name=self.name, copy=False)
+
+    @cache_readonly
+    def _isnan(self) -> np.ndarray:
+        return self._data.isna()

pandas/core/indexes/interval.py

@@ -37,7 +37,6 @@
     is_object_dtype,
     is_scalar,
 )
-from pandas.core.dtypes.missing import isna
 
 from pandas.core.algorithms import take_1d
 from pandas.core.arrays.interval import IntervalArray, _interval_shared_docs
@@ -192,9 +191,6 @@ class IntervalIndex(IntervalMixin, ExtensionIndex):
     # we would like our indexing holder to defer to us
     _defer_to_indexing = True
 
-    # Immutable, so we are able to cache computations like isna in '_mask'
-    _mask = None
-
     _data: IntervalArray
     _values: IntervalArray
 
@@ -342,15 +338,6 @@ def _shallow_copy(
         result._cache = self._cache
         return result
 
-    @cache_readonly
-    def _isnan(self):
-        """
-        Return a mask indicating if each value is NA.
-        """
-        if self._mask is None:
-            self._mask = isna(self.left)
-        return self._mask
-
     @cache_readonly
     def _engine(self):
         left = self._maybe_convert_i8(self.left)