From 48ee962bb09a55484a8f1fa2b27ef478bd194956 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Torsten=20W=C3=B6rtwein?= <twoertwein@gmail.com>
Date: Mon, 7 Aug 2023 22:08:26 -0400
Subject: [PATCH 1/2] TYP:ExtensionDtype.name/type as ClassVar

---
 pandas/core/arrays/boolean.py  |  3 ++-
 pandas/core/arrays/floating.py | 10 ++++++----
 pandas/core/arrays/integer.py  | 34 ++++++++++++++++++----------------
 pandas/core/arrays/masked.py   |  1 +
 pandas/core/arrays/string_.py  |  5 ++---
 pandas/core/dtypes/base.py     | 32 ++++++++++++++------------------
 pandas/core/dtypes/dtypes.py   | 14 +++++---------
 7 files changed, 48 insertions(+), 51 deletions(-)

diff --git a/pandas/core/arrays/boolean.py b/pandas/core/arrays/boolean.py
index 43344f04085ae..04e6f0a0bcdde 100644
--- a/pandas/core/arrays/boolean.py
+++ b/pandas/core/arrays/boolean.py
@@ -3,6 +3,7 @@
 import numbers
 from typing import (
     TYPE_CHECKING,
+    ClassVar,
     cast,
 )
 
@@ -60,7 +61,7 @@ class BooleanDtype(BaseMaskedDtype):
     BooleanDtype
     """
 
-    name = "boolean"
+    name: ClassVar[str] = "boolean"
 
     # https://github.com/python/mypy/issues/4125
     # error: Signature of "type" incompatible with supertype "BaseMaskedDtype"
diff --git a/pandas/core/arrays/floating.py b/pandas/core/arrays/floating.py
index bd3c03f9218d4..c85a5479f3e58 100644
--- a/pandas/core/arrays/floating.py
+++ b/pandas/core/arrays/floating.py
@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+from typing import ClassVar
+
 import numpy as np
 
 from pandas.core.dtypes.base import register_extension_dtype
@@ -155,15 +157,15 @@ class FloatingArray(NumericArray):
 
 @register_extension_dtype
 class Float32Dtype(FloatingDtype):
-    type = np.float32
-    name = "Float32"
+    type: ClassVar[type[np.float32]] = np.float32
+    name: ClassVar[str] = "Float32"
     __doc__ = _dtype_docstring.format(dtype="float32")
 
 
 @register_extension_dtype
 class Float64Dtype(FloatingDtype):
-    type = np.float64
-    name = "Float64"
+    type: ClassVar[type[np.float64]] = np.float64
+    name: ClassVar[str] = "Float64"
     __doc__ = _dtype_docstring.format(dtype="float64")
 
 
diff --git a/pandas/core/arrays/integer.py b/pandas/core/arrays/integer.py
index 0e6e7a484bbb7..55a84214be532 100644
--- a/pandas/core/arrays/integer.py
+++ b/pandas/core/arrays/integer.py
@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+from typing import ClassVar
+
 import numpy as np
 
 from pandas.core.dtypes.base import register_extension_dtype
@@ -204,57 +206,57 @@ class IntegerArray(NumericArray):
 
 @register_extension_dtype
 class Int8Dtype(IntegerDtype):
-    type = np.int8
-    name = "Int8"
+    type: ClassVar[type[np.int8]] = np.int8
+    name: ClassVar[str] = "Int8"
     __doc__ = _dtype_docstring.format(dtype="int8")
 
 
 @register_extension_dtype
 class Int16Dtype(IntegerDtype):
-    type = np.int16
-    name = "Int16"
+    type: ClassVar[type[np.int16]] = np.int16
+    name: ClassVar[str] = "Int16"
     __doc__ = _dtype_docstring.format(dtype="int16")
 
 
 @register_extension_dtype
 class Int32Dtype(IntegerDtype):
-    type = np.int32
-    name = "Int32"
+    type: ClassVar[type[np.int32]] = np.int32
+    name: ClassVar[str] = "Int32"
     __doc__ = _dtype_docstring.format(dtype="int32")
 
 
 @register_extension_dtype
 class Int64Dtype(IntegerDtype):
-    type = np.int64
-    name = "Int64"
+    type: ClassVar[type[np.int64]] = np.int64
+    name: ClassVar[str] = "Int64"
     __doc__ = _dtype_docstring.format(dtype="int64")
 
 
 @register_extension_dtype
 class UInt8Dtype(IntegerDtype):
-    type = np.uint8
-    name = "UInt8"
+    type: ClassVar[type[np.uint8]] = np.uint8
+    name: ClassVar[str] = "UInt8"
     __doc__ = _dtype_docstring.format(dtype="uint8")
 
 
 @register_extension_dtype
 class UInt16Dtype(IntegerDtype):
-    type = np.uint16
-    name = "UInt16"
+    type: ClassVar[type[np.uint16]] = np.uint16
+    name: ClassVar[str] = "UInt16"
     __doc__ = _dtype_docstring.format(dtype="uint16")
 
 
 @register_extension_dtype
 class UInt32Dtype(IntegerDtype):
-    type = np.uint32
-    name = "UInt32"
+    type: ClassVar[type[np.uint32]] = np.uint32
+    name: ClassVar[str] = "UInt32"
     __doc__ = _dtype_docstring.format(dtype="uint32")
 
 
 @register_extension_dtype
 class UInt64Dtype(IntegerDtype):
-    type = np.uint64
-    name = "UInt64"
+    type: ClassVar[type[np.uint64]] = np.uint64
+    name: ClassVar[str] = "UInt64"
     __doc__ = _dtype_docstring.format(dtype="uint64")
 
 
diff --git a/pandas/core/arrays/masked.py b/pandas/core/arrays/masked.py
index bec875f2bbfa1..a14de26e1ff6c 100644
--- a/pandas/core/arrays/masked.py
+++ b/pandas/core/arrays/masked.py
@@ -4,6 +4,7 @@
     TYPE_CHECKING,
     Any,
     Callable,
+    ClassVar,
     Literal,
     overload,
 )
diff --git a/pandas/core/arrays/string_.py b/pandas/core/arrays/string_.py
index 25f1c2ec6ce4f..131222dff5765 100644
--- a/pandas/core/arrays/string_.py
+++ b/pandas/core/arrays/string_.py
@@ -2,6 +2,7 @@
 
 from typing import (
     TYPE_CHECKING,
+    ClassVar,
     Literal,
 )
 
@@ -118,9 +119,7 @@ def __init__(self, storage=None) -> None:
             )
         self.storage = storage
 
-    @property
-    def type(self) -> type[str]:
-        return str
+    type: ClassVar[type_t[str]] = str
 
     @classmethod
     def construct_from_string(cls, string):
diff --git a/pandas/core/dtypes/base.py b/pandas/core/dtypes/base.py
index bc776434b2e6e..db4ee4c7e13ec 100644
--- a/pandas/core/dtypes/base.py
+++ b/pandas/core/dtypes/base.py
@@ -6,6 +6,7 @@
 from typing import (
     TYPE_CHECKING,
     Any,
+    ClassVar,
     TypeVar,
     cast,
     overload,
@@ -158,17 +159,15 @@ def na_value(self) -> object:
         """
         return np.nan
 
-    @property
-    def type(self) -> type_t[Any]:
-        """
-        The scalar type for the array, e.g. ``int``
+    """
+    The scalar type for the array, e.g. ``int``
 
-        It's expected ``ExtensionArray[item]`` returns an instance
-        of ``ExtensionDtype.type`` for scalar ``item``, assuming
-        that value is valid (not NA). NA values do not need to be
-        instances of `type`.
-        """
-        raise AbstractMethodError(self)
+    It's expected ``ExtensionArray[item]`` returns an instance
+    of ``ExtensionDtype.type`` for scalar ``item``, assuming
+    that value is valid (not NA). NA values do not need to be
+    instances of `type`.
+    """
+    type: ClassVar[type] = NotImplementedError
 
     @property
     def kind(self) -> str:
@@ -186,14 +185,12 @@ def kind(self) -> str:
         """
         return "O"
 
-    @property
-    def name(self) -> str:
-        """
-        A string identifying the data type.
+    """
+    A string identifying the data type.
 
-        Will be used for display in, e.g. ``Series.dtype``
-        """
-        raise AbstractMethodError(self)
+    Will be used for display in, e.g. ``Series.dtype``
+    """
+    name: ClassVar[str] = "NotImplementedError"
 
     @property
     def names(self) -> list[str] | None:
@@ -410,7 +407,6 @@ def _is_immutable(self) -> bool:
 class StorageExtensionDtype(ExtensionDtype):
     """ExtensionDtype that may be backed by more than one implementation."""
 
-    name: str
     _metadata = ("storage",)
 
     def __init__(self, storage: str | None = None) -> None:
diff --git a/pandas/core/dtypes/dtypes.py b/pandas/core/dtypes/dtypes.py
index 53f0fb2843653..accbfbe5e6b2a 100644
--- a/pandas/core/dtypes/dtypes.py
+++ b/pandas/core/dtypes/dtypes.py
@@ -14,6 +14,7 @@
 from typing import (
     TYPE_CHECKING,
     Any,
+    ClassVar,
     cast,
 )
 import warnings
@@ -103,7 +104,6 @@ class PandasExtensionDtype(ExtensionDtype):
     THIS IS NOT A REAL NUMPY DTYPE
     """
 
-    type: Any
     kind: Any
     # The Any type annotations above are here only because mypy seems to have a
     # problem dealing with multiple inheritance from PandasExtensionDtype
@@ -200,7 +200,7 @@ class CategoricalDtype(PandasExtensionDtype, ExtensionDtype):
 
     # TODO: Document public vs. private API
     name = "category"
-    type: type[CategoricalDtypeType] = CategoricalDtypeType
+    type: ClassVar[type[CategoricalDtypeType]] = CategoricalDtypeType
     kind: str_type = "O"
     str = "|O08"
     base = np.dtype("O")
@@ -711,7 +711,7 @@ class DatetimeTZDtype(PandasExtensionDtype):
     datetime64[ns, Europe/Paris]
     """
 
-    type: type[Timestamp] = Timestamp
+    type: ClassVar[type[Timestamp]] = Timestamp
     kind: str_type = "M"
     num = 101
     _metadata = ("unit", "tz")
@@ -941,7 +941,7 @@ class PeriodDtype(PeriodDtypeBase, PandasExtensionDtype):
     period[M]
     """
 
-    type: type[Period] = Period
+    type: ClassVar[type[Period]] = Period
     kind: str_type = "O"
     str = "|O08"
     base = np.dtype("O")
@@ -1285,9 +1285,7 @@ def construct_from_string(cls, string: str_type) -> IntervalDtype:
         )
         raise TypeError(msg)
 
-    @property
-    def type(self) -> type[Interval]:
-        return Interval
+    type: ClassVar[type[Interval]] = Interval
 
     def __str__(self) -> str_type:
         if self.subtype is None:
@@ -1488,9 +1486,7 @@ class BaseMaskedDtype(ExtensionDtype):
     Base class for dtypes for BaseMaskedArray subclasses.
     """
 
-    name: str
     base = None
-    type: type
 
     @property
     def na_value(self) -> libmissing.NAType:

From 50141835d2e2f78bed5271a078bd8543a7bb3fef Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Torsten=20W=C3=B6rtwein?= <twoertwein@gmail.com>
Date: Wed, 9 Aug 2023 10:30:29 -0400
Subject: [PATCH 2/2] no code changes; only .name

---
 pandas/core/arrays/floating.py |  4 ++--
 pandas/core/arrays/integer.py  | 16 ++++++++--------
 pandas/core/arrays/masked.py   |  1 -
 pandas/core/arrays/string_.py  |  8 ++++++--
 pandas/core/dtypes/base.py     | 32 ++++++++++++++++++--------------
 pandas/core/dtypes/dtypes.py   | 13 ++++++++-----
 6 files changed, 42 insertions(+), 32 deletions(-)

diff --git a/pandas/core/arrays/floating.py b/pandas/core/arrays/floating.py
index c85a5479f3e58..40c8347c6f1a3 100644
--- a/pandas/core/arrays/floating.py
+++ b/pandas/core/arrays/floating.py
@@ -157,14 +157,14 @@ class FloatingArray(NumericArray):
 
 @register_extension_dtype
 class Float32Dtype(FloatingDtype):
-    type: ClassVar[type[np.float32]] = np.float32
+    type = np.float32
     name: ClassVar[str] = "Float32"
     __doc__ = _dtype_docstring.format(dtype="float32")
 
 
 @register_extension_dtype
 class Float64Dtype(FloatingDtype):
-    type: ClassVar[type[np.float64]] = np.float64
+    type = np.float64
     name: ClassVar[str] = "Float64"
     __doc__ = _dtype_docstring.format(dtype="float64")
 
diff --git a/pandas/core/arrays/integer.py b/pandas/core/arrays/integer.py
index 55a84214be532..f9384e25ba9d9 100644
--- a/pandas/core/arrays/integer.py
+++ b/pandas/core/arrays/integer.py
@@ -206,56 +206,56 @@ class IntegerArray(NumericArray):
 
 @register_extension_dtype
 class Int8Dtype(IntegerDtype):
-    type: ClassVar[type[np.int8]] = np.int8
+    type = np.int8
     name: ClassVar[str] = "Int8"
     __doc__ = _dtype_docstring.format(dtype="int8")
 
 
 @register_extension_dtype
 class Int16Dtype(IntegerDtype):
-    type: ClassVar[type[np.int16]] = np.int16
+    type = np.int16
     name: ClassVar[str] = "Int16"
     __doc__ = _dtype_docstring.format(dtype="int16")
 
 
 @register_extension_dtype
 class Int32Dtype(IntegerDtype):
-    type: ClassVar[type[np.int32]] = np.int32
+    type = np.int32
     name: ClassVar[str] = "Int32"
     __doc__ = _dtype_docstring.format(dtype="int32")
 
 
 @register_extension_dtype
 class Int64Dtype(IntegerDtype):
-    type: ClassVar[type[np.int64]] = np.int64
+    type = np.int64
     name: ClassVar[str] = "Int64"
     __doc__ = _dtype_docstring.format(dtype="int64")
 
 
 @register_extension_dtype
 class UInt8Dtype(IntegerDtype):
-    type: ClassVar[type[np.uint8]] = np.uint8
+    type = np.uint8
     name: ClassVar[str] = "UInt8"
     __doc__ = _dtype_docstring.format(dtype="uint8")
 
 
 @register_extension_dtype
 class UInt16Dtype(IntegerDtype):
-    type: ClassVar[type[np.uint16]] = np.uint16
+    type = np.uint16
     name: ClassVar[str] = "UInt16"
     __doc__ = _dtype_docstring.format(dtype="uint16")
 
 
 @register_extension_dtype
 class UInt32Dtype(IntegerDtype):
-    type: ClassVar[type[np.uint32]] = np.uint32
+    type = np.uint32
     name: ClassVar[str] = "UInt32"
     __doc__ = _dtype_docstring.format(dtype="uint32")
 
 
 @register_extension_dtype
 class UInt64Dtype(IntegerDtype):
-    type: ClassVar[type[np.uint64]] = np.uint64
+    type = np.uint64
     name: ClassVar[str] = "UInt64"
     __doc__ = _dtype_docstring.format(dtype="uint64")
 
diff --git a/pandas/core/arrays/masked.py b/pandas/core/arrays/masked.py
index a14de26e1ff6c..bec875f2bbfa1 100644
--- a/pandas/core/arrays/masked.py
+++ b/pandas/core/arrays/masked.py
@@ -4,7 +4,6 @@
     TYPE_CHECKING,
     Any,
     Callable,
-    ClassVar,
     Literal,
     overload,
 )
diff --git a/pandas/core/arrays/string_.py b/pandas/core/arrays/string_.py
index 131222dff5765..e4305abc97cbb 100644
--- a/pandas/core/arrays/string_.py
+++ b/pandas/core/arrays/string_.py
@@ -97,7 +97,9 @@ class StringDtype(StorageExtensionDtype):
     string[pyarrow]
     """
 
-    name = "string"
+    # error: Cannot override instance variable (previously declared on
+    # base class "StorageExtensionDtype") with class variable
+    name: ClassVar[str] = "string"  # type: ignore[misc]
 
     #: StringDtype().na_value uses pandas.NA
     @property
@@ -119,7 +121,9 @@ def __init__(self, storage=None) -> None:
             )
         self.storage = storage
 
-    type: ClassVar[type_t[str]] = str
+    @property
+    def type(self) -> type[str]:
+        return str
 
     @classmethod
     def construct_from_string(cls, string):
diff --git a/pandas/core/dtypes/base.py b/pandas/core/dtypes/base.py
index db4ee4c7e13ec..bc776434b2e6e 100644
--- a/pandas/core/dtypes/base.py
+++ b/pandas/core/dtypes/base.py
@@ -6,7 +6,6 @@
 from typing import (
     TYPE_CHECKING,
     Any,
-    ClassVar,
     TypeVar,
     cast,
     overload,
@@ -159,15 +158,17 @@ def na_value(self) -> object:
         """
         return np.nan
 
-    """
-    The scalar type for the array, e.g. ``int``
+    @property
+    def type(self) -> type_t[Any]:
+        """
+        The scalar type for the array, e.g. ``int``
 
-    It's expected ``ExtensionArray[item]`` returns an instance
-    of ``ExtensionDtype.type`` for scalar ``item``, assuming
-    that value is valid (not NA). NA values do not need to be
-    instances of `type`.
-    """
-    type: ClassVar[type] = NotImplementedError
+        It's expected ``ExtensionArray[item]`` returns an instance
+        of ``ExtensionDtype.type`` for scalar ``item``, assuming
+        that value is valid (not NA). NA values do not need to be
+        instances of `type`.
+        """
+        raise AbstractMethodError(self)
 
     @property
     def kind(self) -> str:
@@ -185,12 +186,14 @@ def kind(self) -> str:
         """
         return "O"
 
-    """
-    A string identifying the data type.
+    @property
+    def name(self) -> str:
+        """
+        A string identifying the data type.
 
-    Will be used for display in, e.g. ``Series.dtype``
-    """
-    name: ClassVar[str] = "NotImplementedError"
+        Will be used for display in, e.g. ``Series.dtype``
+        """
+        raise AbstractMethodError(self)
 
     @property
     def names(self) -> list[str] | None:
@@ -407,6 +410,7 @@ def _is_immutable(self) -> bool:
 class StorageExtensionDtype(ExtensionDtype):
     """ExtensionDtype that may be backed by more than one implementation."""
 
+    name: str
     _metadata = ("storage",)
 
     def __init__(self, storage: str | None = None) -> None:
diff --git a/pandas/core/dtypes/dtypes.py b/pandas/core/dtypes/dtypes.py
index accbfbe5e6b2a..368e499d3da33 100644
--- a/pandas/core/dtypes/dtypes.py
+++ b/pandas/core/dtypes/dtypes.py
@@ -14,7 +14,6 @@
 from typing import (
     TYPE_CHECKING,
     Any,
-    ClassVar,
     cast,
 )
 import warnings
@@ -104,6 +103,7 @@ class PandasExtensionDtype(ExtensionDtype):
     THIS IS NOT A REAL NUMPY DTYPE
     """
 
+    type: Any
     kind: Any
     # The Any type annotations above are here only because mypy seems to have a
     # problem dealing with multiple inheritance from PandasExtensionDtype
@@ -200,7 +200,7 @@ class CategoricalDtype(PandasExtensionDtype, ExtensionDtype):
 
     # TODO: Document public vs. private API
     name = "category"
-    type: ClassVar[type[CategoricalDtypeType]] = CategoricalDtypeType
+    type: type[CategoricalDtypeType] = CategoricalDtypeType
     kind: str_type = "O"
     str = "|O08"
     base = np.dtype("O")
@@ -711,7 +711,7 @@ class DatetimeTZDtype(PandasExtensionDtype):
     datetime64[ns, Europe/Paris]
     """
 
-    type: ClassVar[type[Timestamp]] = Timestamp
+    type: type[Timestamp] = Timestamp
     kind: str_type = "M"
     num = 101
     _metadata = ("unit", "tz")
@@ -941,7 +941,7 @@ class PeriodDtype(PeriodDtypeBase, PandasExtensionDtype):
     period[M]
     """
 
-    type: ClassVar[type[Period]] = Period
+    type: type[Period] = Period
     kind: str_type = "O"
     str = "|O08"
     base = np.dtype("O")
@@ -1285,7 +1285,9 @@ def construct_from_string(cls, string: str_type) -> IntervalDtype:
         )
         raise TypeError(msg)
 
-    type: ClassVar[type[Interval]] = Interval
+    @property
+    def type(self) -> type[Interval]:
+        return Interval
 
     def __str__(self) -> str_type:
         if self.subtype is None:
@@ -1487,6 +1489,7 @@ class BaseMaskedDtype(ExtensionDtype):
     """
 
     base = None
+    type: type
 
     @property
     def na_value(self) -> libmissing.NAType: