Remove real, imag, astype methods from NamedArray (#8295)

* remove imag / real / astype

* Remove real, imag and astype

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* add imag, real functions

* Update variable.py

* Update utils.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update utils.py

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: Illviljan

xarray/core/variable.py

@@ -2400,6 +2400,28 @@ def notnull(self, keep_attrs: bool | None = None):
             keep_attrs=keep_attrs,
         )
 
+    @property
+    def real(self):
+        """
+        The real part of the variable.
+
+        See Also
+        --------
+        numpy.ndarray.real
+        """
+        return self._replace(data=self.data.real)
+
+    @property
+    def imag(self):
+        """
+        The imaginary part of the variable.
+
+        See Also
+        --------
+        numpy.ndarray.imag
+        """
+        return self._replace(data=self.data.imag)
+
     def __array_wrap__(self, obj, context=None):
         return Variable(self.dims, obj)
 

xarray/namedarray/core.py

@@ -14,6 +14,7 @@
     Default,
     T_DuckArray,
     _default,
+    astype,
     is_chunked_duck_array,
     is_duck_array,
     is_duck_dask_array,
@@ -245,28 +246,6 @@ def data(self, data: T_DuckArray | np.typing.ArrayLike) -> None:
         self._check_shape(data)
         self._data = data
 
-    @property
-    def real(self) -> Self:
-        """
-        The real part of the NamedArray.
-
-        See Also
-        --------
-        numpy.ndarray.real
-        """
-        return self._replace(data=self.data.real)
-
-    @property
-    def imag(self) -> Self:
-        """
-        The imaginary part of the NamedArray.
-
-        See Also
-        --------
-        numpy.ndarray.imag
-        """
-        return self._replace(data=self.data.imag)
-
     def __dask_tokenize__(self) -> Hashable:
         # Use v.data, instead of v._data, in order to cope with the wrappers
         # around NetCDF and the like
@@ -497,7 +476,7 @@ def _as_sparse(
         except AttributeError as exc:
             raise ValueError(f"{sparse_format} is not a valid sparse format") from exc
 
-        data = as_sparse(self.data.astype(dtype), fill_value=fill_value)
+        data = as_sparse(astype(self.data, dtype), fill_value=fill_value)
         return self._replace(data=data)
 
     def _to_dense(self) -> Self:

xarray/namedarray/utils.py

@@ -4,6 +4,7 @@
 import sys
 from collections.abc import Hashable
 from enum import Enum
+from types import ModuleType
 from typing import TYPE_CHECKING, Any, Final, Protocol, TypeVar
 
 import numpy as np
@@ -15,9 +16,9 @@
         from typing_extensions import TypeGuard
 
     if sys.version_info >= (3, 11):
-        from typing import Self
+        pass
     else:
-        from typing_extensions import Self
+        pass
 
     try:
         from dask.array import Array as DaskArray
@@ -29,7 +30,7 @@
 
 # https://stackoverflow.com/questions/74633074/how-to-type-hint-a-generic-numpy-array
 T_DType_co = TypeVar("T_DType_co", bound=np.dtype[np.generic], covariant=True)
-# T_DType = TypeVar("T_DType", bound=np.dtype[np.generic])
+T_DType = TypeVar("T_DType", bound=np.dtype[np.generic])
 
 
 class _Array(Protocol[T_DType_co]):
@@ -41,17 +42,6 @@ def dtype(self) -> T_DType_co:
     def shape(self) -> tuple[int, ...]:
         ...
 
-    @property
-    def real(self) -> Self:
-        ...
-
-    @property
-    def imag(self) -> Self:
-        ...
-
-    def astype(self, dtype: np.typing.DTypeLike) -> Self:
-        ...
-
     # TODO: numpy doesn't use any inputs:
     # https://github.com/numpy/numpy/blob/v1.24.3/numpy/_typing/_array_like.py#L38
     def __array__(self) -> np.ndarray[Any, T_DType_co]:
@@ -161,3 +151,30 @@ def __dask_tokenize__(self) -> Hashable:
         from dask.base import normalize_token
 
         return normalize_token((type(self), self._value))  # type: ignore[no-any-return]
+
+
+# %% Array API functions
+def get_array_namespace(x: _Array[Any]) -> ModuleType:
+    if hasattr(x, "__array_namespace__"):
+        return x.__array_namespace__()  # type: ignore[no-any-return]
+    else:
+        return np
+
+
+def astype(x: _Array[Any], dtype: T_DType, /, *, copy: bool = True) -> _Array[T_DType]:
+    if hasattr(x, "__array_namespace__"):
+        xp = x.__array_namespace__()
+        return xp.astype(x, dtype, copy=copy)  # type: ignore[no-any-return]
+
+    # np.astype doesn't exist yet:
+    return x.astype(dtype, copy=copy)  # type: ignore[no-any-return, attr-defined]
+
+
+def imag(x: _Array[Any], /) -> _Array[Any]:
+    xp = get_array_namespace(x)
+    return xp.imag(x)  # type: ignore[no-any-return]
+
+
+def real(x: _Array[Any], /) -> _Array[Any]:
+    xp = get_array_namespace(x)
+    return xp.real(x)  # type: ignore[no-any-return]