TYP: Use Self for type checking (remaining locations) (#51524)

* TYP: Use Self for type checking (pandas/core/internals/)

* TYP: Use Self for type checking (remaining locations/)

Author: topper-123

pandas/core/base.py

@@ -12,7 +12,6 @@
     Hashable,
     Iterator,
     Literal,
-    TypeVar,
     cast,
     final,
     overload,
@@ -29,6 +28,7 @@
     DtypeObj,
     IndexLabel,
     NDFrameT,
+    Self,
     Shape,
     npt,
 )
@@ -91,8 +91,6 @@
     "duplicated": "IndexOpsMixin",
 }
 
-_T = TypeVar("_T", bound="IndexOpsMixin")
-
 
 class PandasObject(DirNamesMixin):
     """
@@ -285,7 +283,7 @@ def _values(self) -> ExtensionArray | np.ndarray:
         raise AbstractMethodError(self)
 
     @final
-    def transpose(self: _T, *args, **kwargs) -> _T:
+    def transpose(self, *args, **kwargs) -> Self:
         """
         Return the transpose, which is by definition self.
 

pandas/core/dtypes/base.py

@@ -26,6 +26,7 @@
 if TYPE_CHECKING:
     from pandas._typing import (
         DtypeObj,
+        Self,
         Shape,
         npt,
         type_t,
@@ -228,9 +229,7 @@ def empty(self, shape: Shape) -> type_t[ExtensionArray]:
         return cls._empty(shape, dtype=self)
 
     @classmethod
-    def construct_from_string(
-        cls: type_t[ExtensionDtypeT], string: str
-    ) -> ExtensionDtypeT:
+    def construct_from_string(cls, string: str) -> Self:
         r"""
         Construct this type from a string.
 

pandas/core/indexing.py

@@ -6,7 +6,6 @@
     TYPE_CHECKING,
     Hashable,
     Sequence,
-    TypeVar,
     cast,
     final,
 )
@@ -78,15 +77,14 @@
     from pandas._typing import (
         Axis,
         AxisInt,
+        Self,
     )
 
     from pandas import (
         DataFrame,
         Series,
     )
 
-_LocationIndexerT = TypeVar("_LocationIndexerT", bound="_LocationIndexer")
-
 # "null slice"
 _NS = slice(None, None)
 _one_ellipsis_message = "indexer may only contain one '...' entry"
@@ -669,9 +667,7 @@ class _LocationIndexer(NDFrameIndexerBase):
     _takeable: bool
 
     @final
-    def __call__(
-        self: _LocationIndexerT, axis: Axis | None = None
-    ) -> _LocationIndexerT:
+    def __call__(self, axis: Axis | None = None) -> Self:
         # we need to return a copy of ourselves
         new_self = type(self)(self.name, self.obj)
 

pandas/core/internals/base.py

@@ -7,7 +7,6 @@
 from typing import (
     TYPE_CHECKING,
     Literal,
-    TypeVar,
     final,
 )
 
@@ -31,9 +30,9 @@
         ArrayLike,
         AxisInt,
         DtypeObj,
+        Self,
         Shape,
     )
-T = TypeVar("T", bound="DataManager")
 
 
 class DataManager(PandasObject):
@@ -75,25 +74,25 @@ def _validate_set_axis(self, axis: AxisInt, new_labels: Index) -> None:
             )
 
     def reindex_indexer(
-        self: T,
+        self,
         new_axis,
         indexer,
         axis: AxisInt,
         fill_value=None,
         allow_dups: bool = False,
         copy: bool = True,
         only_slice: bool = False,
-    ) -> T:
+    ) -> Self:
         raise AbstractMethodError(self)
 
     @final
     def reindex_axis(
-        self: T,
+        self,
         new_index: Index,
         axis: AxisInt,
         fill_value=None,
         only_slice: bool = False,
-    ) -> T:
+    ) -> Self:
         """
         Conform data manager to new index.
         """
@@ -108,7 +107,7 @@ def reindex_axis(
             only_slice=only_slice,
         )
 
-    def _equal_values(self: T, other: T) -> bool:
+    def _equal_values(self, other: Self) -> bool:
         """
         To be implemented by the subclasses. Only check the column values
         assuming shape and indexes have already been checked.
@@ -132,15 +131,15 @@ def equals(self, other: object) -> bool:
         return self._equal_values(other)
 
     def apply(
-        self: T,
+        self,
         f,
         align_keys: list[str] | None = None,
         **kwargs,
-    ) -> T:
+    ) -> Self:
         raise AbstractMethodError(self)
 
     @final
-    def isna(self: T, func) -> T:
+    def isna(self, func) -> Self:
         return self.apply("apply", func=func)
 
     # --------------------------------------------------------------------
@@ -149,7 +148,7 @@ def isna(self: T, func) -> T:
     def is_consolidated(self) -> bool:
         return True
 
-    def consolidate(self: T) -> T:
+    def consolidate(self) -> Self:
         return self
 
     def _consolidate_inplace(self) -> None: