TYP: copy method of EAs (pandas-dev#37816)

pandas/core/arrays/_mixins.py

@@ -20,7 +20,9 @@
 from pandas.core.construction import extract_array
 from pandas.core.indexers import check_array_indexer
 
-_T = TypeVar("_T", bound="NDArrayBackedExtensionArray")
+NDArrayBackedExtensionArrayT = TypeVar(
+    "NDArrayBackedExtensionArrayT", bound="NDArrayBackedExtensionArray"
+)
 
 
 class NDArrayBackedExtensionArray(ExtensionArray):
@@ -30,7 +32,9 @@ class NDArrayBackedExtensionArray(ExtensionArray):
 
     _ndarray: np.ndarray
 
-    def _from_backing_data(self: _T, arr: np.ndarray) -> _T:
+    def _from_backing_data(
+        self: NDArrayBackedExtensionArrayT, arr: np.ndarray
+    ) -> NDArrayBackedExtensionArrayT:
         """
         Construct a new ExtensionArray `new_array` with `arr` as its _ndarray.
 
@@ -52,13 +56,13 @@ def _validate_scalar(self, value):
     # ------------------------------------------------------------------------
 
     def take(
-        self: _T,
+        self: NDArrayBackedExtensionArrayT,
         indices: Sequence[int],
         *,
         allow_fill: bool = False,
         fill_value: Any = None,
         axis: int = 0,
-    ) -> _T:
+    ) -> NDArrayBackedExtensionArrayT:
         if allow_fill:
             fill_value = self._validate_fill_value(fill_value)
 
@@ -113,16 +117,20 @@ def size(self) -> int:
     def nbytes(self) -> int:
         return self._ndarray.nbytes
 
-    def reshape(self: _T, *args, **kwargs) -> _T:
+    def reshape(
+        self: NDArrayBackedExtensionArrayT, *args, **kwargs
+    ) -> NDArrayBackedExtensionArrayT:
         new_data = self._ndarray.reshape(*args, **kwargs)
         return self._from_backing_data(new_data)
 
-    def ravel(self: _T, *args, **kwargs) -> _T:
+    def ravel(
+        self: NDArrayBackedExtensionArrayT, *args, **kwargs
+    ) -> NDArrayBackedExtensionArrayT:
         new_data = self._ndarray.ravel(*args, **kwargs)
         return self._from_backing_data(new_data)
 
     @property
-    def T(self: _T) -> _T:
+    def T(self: NDArrayBackedExtensionArrayT) -> NDArrayBackedExtensionArrayT:
         new_data = self._ndarray.T
         return self._from_backing_data(new_data)
 
@@ -138,11 +146,13 @@ def equals(self, other) -> bool:
     def _values_for_argsort(self):
         return self._ndarray
 
-    def copy(self: _T) -> _T:
+    def copy(self: NDArrayBackedExtensionArrayT) -> NDArrayBackedExtensionArrayT:
         new_data = self._ndarray.copy()
         return self._from_backing_data(new_data)
 
-    def repeat(self: _T, repeats, axis=None) -> _T:
+    def repeat(
+        self: NDArrayBackedExtensionArrayT, repeats, axis=None
+    ) -> NDArrayBackedExtensionArrayT:
         """
         Repeat elements of an array.
 
@@ -154,7 +164,7 @@ def repeat(self: _T, repeats, axis=None) -> _T:
         new_data = self._ndarray.repeat(repeats, axis=axis)
         return self._from_backing_data(new_data)
 
-    def unique(self: _T) -> _T:
+    def unique(self: NDArrayBackedExtensionArrayT) -> NDArrayBackedExtensionArrayT:
         new_data = unique(self._ndarray)
         return self._from_backing_data(new_data)
 
@@ -216,7 +226,9 @@ def __getitem__(self, key):
         return result
 
     @doc(ExtensionArray.fillna)
-    def fillna(self: _T, value=None, method=None, limit=None) -> _T:
+    def fillna(
+        self: NDArrayBackedExtensionArrayT, value=None, method=None, limit=None
+    ) -> NDArrayBackedExtensionArrayT:
         value, method = validate_fillna_kwargs(value, method)
 
         mask = self.isna()

pandas/core/arrays/base.py

@@ -12,7 +12,7 @@
 import numpy as np
 
 from pandas._libs import lib
-from pandas._typing import ArrayLike, Shape
+from pandas._typing import ArrayLike, Shape, TypeVar
 from pandas.compat import set_function_name
 from pandas.compat.numpy import function as nv
 from pandas.errors import AbstractMethodError
@@ -37,6 +37,8 @@
 
 _extension_array_shared_docs: Dict[str, str] = dict()
 
+ExtensionArrayT = TypeVar("ExtensionArrayT", bound="ExtensionArray")
+
 
 class ExtensionArray:
     """
@@ -1016,7 +1018,7 @@ def take(self, indices, allow_fill=False, fill_value=None):
         # pandas.api.extensions.take
         raise AbstractMethodError(self)
 
-    def copy(self) -> "ExtensionArray":
+    def copy(self: ExtensionArrayT) -> ExtensionArrayT:
         """
         Return a copy of the array.
 

pandas/core/arrays/interval.py

@@ -1,7 +1,7 @@
 import operator
 from operator import le, lt
 import textwrap
-from typing import TYPE_CHECKING, Optional, Tuple, Union, cast
+from typing import TYPE_CHECKING, Optional, Tuple, TypeVar, Union, cast
 
 import numpy as np
 
@@ -56,6 +56,8 @@
     from pandas import Index
     from pandas.core.arrays import DatetimeArray, TimedeltaArray
 
+IntervalArrayT = TypeVar("IntervalArrayT", bound="IntervalArray")
+
 _interval_shared_docs = {}
 
 _shared_docs_kwargs = dict(
@@ -745,7 +747,7 @@ def _concat_same_type(cls, to_concat):
         combined = _get_combined_data(left, right)  # TODO: 1-stage concat
         return cls._simple_new(combined, closed=closed)
 
-    def copy(self):
+    def copy(self: IntervalArrayT) -> IntervalArrayT:
         """
         Return a copy of the array.
 

pandas/core/arrays/sparse/array.py

@@ -4,7 +4,7 @@
 from collections import abc
 import numbers
 import operator
-from typing import Any, Callable, Union
+from typing import Any, Callable, Type, TypeVar, Union
 import warnings
 
 import numpy as np
@@ -56,6 +56,7 @@
 # ----------------------------------------------------------------------------
 # Array
 
+SparseArrayT = TypeVar("SparseArrayT", bound="SparseArray")
 
 _sparray_doc_kwargs = dict(klass="SparseArray")
 
@@ -397,8 +398,11 @@ def __init__(
 
     @classmethod
     def _simple_new(
-        cls, sparse_array: np.ndarray, sparse_index: SparseIndex, dtype: SparseDtype
-    ) -> "SparseArray":
+        cls: Type[SparseArrayT],
+        sparse_array: np.ndarray,
+        sparse_index: SparseIndex,
+        dtype: SparseDtype,
+    ) -> SparseArrayT:
         new = object.__new__(cls)
         new._sparse_index = sparse_index
         new._sparse_values = sparse_array
@@ -937,7 +941,7 @@ def searchsorted(self, v, side="left", sorter=None):
         v = np.asarray(v)
         return np.asarray(self, dtype=self.dtype.subtype).searchsorted(v, side, sorter)
 
-    def copy(self):
+    def copy(self: SparseArrayT) -> SparseArrayT:
         values = self.sp_values.copy()
         return self._simple_new(values, self.sp_index, self.dtype)