ENH: EA._hasnans, EADtype.empty

pandas/core/arrays/base.py

@@ -425,7 +425,7 @@ def __contains__(self, item: object) -> bool | np.bool_:
             if not self._can_hold_na:
                 return False
             elif item is self.dtype.na_value or isinstance(item, self.dtype.type):
-                return self.isna().any()
+                return self._hasnans
             else:
                 return False
         else:
@@ -603,6 +603,16 @@ def isna(self) -> np.ndarray | ExtensionArraySupportsAnyAll:
         """
         raise AbstractMethodError(self)
 
+    @property
+    def _hasnans(self) -> bool:
+        # GH#22680
+        """
+        Equivalent to `self.isna().any()`.
+
+        Some ExtensionArray subclasses may be able to optimize this check.
+        """
+        return self.isna().any()
+
     def _values_for_argsort(self) -> np.ndarray:
         """
         Return values for sorting.
@@ -686,7 +696,7 @@ def argmin(self, skipna: bool = True) -> int:
         ExtensionArray.argmax
         """
         validate_bool_kwarg(skipna, "skipna")
-        if not skipna and self.isna().any():
+        if not skipna and self._hasnans:
             raise NotImplementedError
         return nargminmax(self, "argmin")
 
@@ -710,7 +720,7 @@ def argmax(self, skipna: bool = True) -> int:
         ExtensionArray.argmin
         """
         validate_bool_kwarg(skipna, "skipna")
-        if not skipna and self.isna().any():
+        if not skipna and self._hasnans:
             raise NotImplementedError
         return nargminmax(self, "argmax")
 

pandas/core/dtypes/base.py

@@ -17,6 +17,7 @@
 from pandas._libs.hashtable import object_hash
 from pandas._typing import (
     DtypeObj,
+    Shape,
     npt,
     type_t,
 )
@@ -208,6 +209,19 @@ def construct_array_type(cls) -> type_t[ExtensionArray]:
         """
         raise AbstractMethodError(cls)
 
+    def empty(self, shape: Shape) -> type_t[ExtensionArray]:
+        """
+        Construct an ExtensionArray of this dtype with the given shape.
+
+        Analogous to numpy.empty.
+
+        Returns
+        -------
+        ExtensionArray
+        """
+        cls = self.construct_array_type()
+        return cls._empty(shape, dtype=self)
+
     @classmethod
     def construct_from_string(
         cls: type_t[ExtensionDtypeT], string: str

pandas/tests/extension/base/constructors.py

@@ -126,6 +126,12 @@ def test_construct_empty_dataframe(self, dtype):
     def test_empty(self, dtype):
         cls = dtype.construct_array_type()
         result = cls._empty((4,), dtype=dtype)
-
         assert isinstance(result, cls)
         assert result.dtype == dtype
+        assert result.shape == (4,)
+
+        # GH#19600 method on ExtensionDtype
+        result2 = dtype.empty((4,))
+        assert isinstance(result2, cls)
+        assert result2.dtype == dtype
+        assert result2.shape == (4,)