Convert ExtensionDtype class objects to instances of that class

pandas/core/dtypes/common.py

@@ -3,6 +3,7 @@
 """
 from __future__ import annotations
 
+import inspect
 from typing import (
     Any,
     Callable,
@@ -1574,9 +1575,8 @@ def get_dtype(arr_or_dtype) -> DtypeObj:
     # fastpath
     elif isinstance(arr_or_dtype, np.dtype):
         return arr_or_dtype
-    elif isinstance(arr_or_dtype, type):
+    elif inspect.isclass(arr_or_dtype) and issubclass(arr_or_dtype, np.generic):
         return np.dtype(arr_or_dtype)
-
     # if we have an array-like
     elif hasattr(arr_or_dtype, "dtype"):
         arr_or_dtype = arr_or_dtype.dtype
@@ -1765,6 +1765,8 @@ def pandas_dtype(dtype) -> DtypeObj:
         return dtype.dtype
     elif isinstance(dtype, (np.dtype, ExtensionDtype)):
         return dtype
+    elif inspect.isclass(dtype) and issubclass(dtype, ExtensionDtype):
+        return dtype()
 
     # registered extension types
     result = registry.find(dtype)

pandas/tests/dtypes/test_common.py

@@ -106,6 +106,48 @@ def test_period_dtype(self, dtype):
         assert com.pandas_dtype(dtype) == PeriodDtype(dtype)
         assert com.pandas_dtype(dtype) == dtype
 
+    @pytest.mark.parametrize(
+        "cls",
+        (
+            pd.BooleanDtype,
+            pd.Int8Dtype,
+            pd.Int16Dtype,
+            pd.Int32Dtype,
+            pd.Int64Dtype,
+            pd.UInt8Dtype,
+            pd.UInt16Dtype,
+            pd.UInt32Dtype,
+            pd.UInt64Dtype,
+            pd.Float32Dtype,
+            pd.Float64Dtype,
+            pd.SparseDtype,
+            pd.StringDtype,
+            IntervalDtype,
+            CategoricalDtype,
+            pytest.param(
+                DatetimeTZDtype,
+                marks=pytest.mark.xfail(reason="must specify TZ", raises=TypeError),
+            ),
+            pytest.param(
+                PeriodDtype,
+                marks=pytest.mark.xfail(
+                    reason="must specify frequency", raises=AttributeError
+                ),
+            ),
+        ),
+    )
+    def test_pd_extension_dtype(self, cls):
+        """
+        TODO: desired behavior?
+
+        For extension dtypes that admit no options OR can be initialized with no args
+        passed, convert the extension dtype class to an instance of that class.
+        """
+        expected = cls()
+        result = com.pandas_dtype(cls)
+
+        assert result == expected
+
 
 dtypes = {
     "datetime_tz": com.pandas_dtype("datetime64[ns, US/Eastern]"),
@@ -558,29 +600,44 @@ def test_is_float_dtype():
     assert com.is_float_dtype(pd.Index([1, 2.0]))
 
 
-def test_is_bool_dtype():
-    assert not com.is_bool_dtype(int)
-    assert not com.is_bool_dtype(str)
-    assert not com.is_bool_dtype(pd.Series([1, 2]))
-    assert not com.is_bool_dtype(pd.Series(["a", "b"], dtype="category"))
-    assert not com.is_bool_dtype(np.array(["a", "b"]))
-    assert not com.is_bool_dtype(pd.Index(["a", "b"]))
-    assert not com.is_bool_dtype("Int64")
-
-    assert com.is_bool_dtype(bool)
-    assert com.is_bool_dtype(np.bool_)
-    assert com.is_bool_dtype(pd.Series([True, False], dtype="category"))
-    assert com.is_bool_dtype(np.array([True, False]))
-    assert com.is_bool_dtype(pd.Index([True, False]))
-
-    assert com.is_bool_dtype(pd.BooleanDtype())
-    assert com.is_bool_dtype(pd.array([True, False, None], dtype="boolean"))
-    assert com.is_bool_dtype("boolean")
+@pytest.mark.parametrize(
+    "value",
+    (
+        True,
+        False,
+        int,
+        str,
+        "Int64",
+        "0 - Name",  # GH39010
+        pd.array(("a", "b")),
+        pd.Index(("a", "b")),
+        pd.Series(("a", "b"), dtype="category"),
+        pd.Series((1, 2)),
+    ),
+)
+def test_is_bool_dtype_returns_false(value):
+    assert com.is_bool_dtype(value) is False
 
 
-def test_is_bool_dtype_numpy_error():
-    # GH39010
-    assert not com.is_bool_dtype("0 - Name")
+@pytest.mark.parametrize(
+    "value",
+    (
+        bool,
+        np.bool_,
+        np.dtype(np.bool_),
+        pd.BooleanDtype,
+        pd.BooleanDtype(),
+        "bool",
+        "boolean",
+        pd.array((True, False)),
+        pd.Index((True, False)),
+        pd.Series((True, False)),
+        pd.Series((True, False), dtype="category"),
+        pd.Series((True, False, None), dtype="boolean"),
+    ),
+)
+def test_is_bool_dtype_returns_true(value):
+    assert com.is_bool_dtype(value) is True
 
 
 @pytest.mark.filterwarnings("ignore:'is_extension_type' is deprecated:FutureWarning")
@@ -674,6 +731,8 @@ def test_is_complex_dtype():
         (PeriodDtype(freq="D"), PeriodDtype(freq="D")),
         ("period[D]", PeriodDtype(freq="D")),
         (IntervalDtype(), IntervalDtype()),
+        (pd.BooleanDtype, pd.BooleanDtype()),
+        (pd.BooleanDtype(), pd.BooleanDtype()),
     ],
 )
 def test_get_dtype(input_param, result):