✨ HasTranspose

Signed-off-by: nstarman <[email protected]>

Author: nstarman

src/array_api_typing/_array.py

@@ -152,6 +152,36 @@ def size(self) -> int | None:
         ...
 
 
+class HasTranspose(Protocol):
+    """Protocol for array classes that support the transpose operation."""
+
+    @property
+    def T(self) -> Self:  # noqa: N802
+        """Transpose of the array.
+
+        The array instance must be two-dimensional. If the array instance is not
+        two-dimensional, an error should be raised.
+
+        Returns:
+            Self: two-dimensional array whose first and last dimensions (axes)
+                are permuted in reverse order relative to original array. The
+                returned array must have the same data type as the original
+                array.
+
+        Notes:
+            Limiting the transpose to two-dimensional arrays (matrices) deviates
+            from the NumPy et al practice of reversing all axes for arrays
+            having more than two-dimensions. This is intentional, as reversing
+            all axes was found to be problematic (e.g., conflicting with the
+            mathematical definition of a transpose which is limited to matrices;
+            not operating on batches of matrices; et cetera). In order to
+            reverse all axes, one is recommended to use the functional
+            `PermuteDims` interface found in this specification.
+
+        """
+        ...
+
+
 class Array(
     # ------ Attributes -------
     HasDType[DTypeT_co],
@@ -160,6 +190,7 @@ class Array(
     HasNDim,
     HasShape,
     HasSize,
+    HasTranspose,
     # ------- Methods ---------
     HasArrayNamespace[NamespaceT_co],
     # -------------------------

tests/integration/test_numpy1p0.pyi

@@ -75,3 +75,7 @@ _: tuple[int | None, ...] = x_i32.shape
 # Check Attribute `.size`
 _: int | None = x_f32.size
 _: int | None = x_i32.size
+
+# Check Attribute `.T`
+_: xpt.Array[dtype[Any]] = x_f32.T
+_: xpt.Array[dtype[Any]] = x_i32.T

tests/integration/test_numpy2p0.pyi

@@ -86,3 +86,8 @@ _: tuple[int | None, ...] = x_b.shape
 _: int | None = x_f32.size
 _: int | None = x_i32.size
 _: int | None = x_b.size
+
+# Check Attribute `.T`
+_: xpt.Array[np.dtype[F32]] = x_f32.T
+_: xpt.Array[np.dtype[I32]] = x_i32.T
+_: xpt.Array[np.dtype[B]] = x_b.T