Add a documentation about slice to PyArray conversion

Author: kngwyu

src/convert.rs

@@ -71,12 +71,27 @@ where
 /// elements there**.
 /// # Example
 /// ```
-/// # fn main() {
 /// use numpy::{PyArray, ToPyArray};
 /// let gil = pyo3::Python::acquire_gil();
 /// let py_array = vec![1, 2, 3].to_pyarray(gil.python());
 /// assert_eq!(py_array.as_slice().unwrap(), &[1, 2, 3]);
-/// # }
+/// ```
+///
+/// This method converts a not-contiguous array to C-order contiguous array.
+/// # Example
+/// ```
+/// use numpy::{PyArray, ToPyArray};
+/// use ndarray::{arr3, s};
+/// let gil = pyo3::Python::acquire_gil();
+/// let py = gil.python();
+/// let a = arr3(&[[[ 1,  2,  3], [ 4,  5,  6]],
+///                [[ 7,  8,  9], [10, 11, 12]]]);
+/// let slice = a.slice(s![.., 0..1, ..]);
+/// let sliced = arr3(&[[[ 1,  2,  3]],
+///                     [[ 7,  8,  9]]]);
+/// let py_slice = slice.to_pyarray(py);
+/// assert_eq!(py_slice.as_array(), sliced);
+/// pyo3::py_run!(py, py_slice, "assert py_slice.flags['C_CONTIGUOUS']");
 /// ```
 pub trait ToPyArray {
     type Item: TypeNum;

tests/to_py.rs

@@ -117,6 +117,7 @@ fn forder_to_pyarray() {
     let fortran_matrix = matrix.reversed_axes();
     let fmat_py = fortran_matrix.to_pyarray(py);
     assert_eq!(fmat_py.as_array(), array![[0, 2, 4, 6], [1, 3, 5, 7]],);
+    pyo3::py_run!(py, fmat_py, "assert fmat_py.flags['F_CONTIGUOUS']")
 }
 
 #[test]
@@ -127,4 +128,16 @@ fn slice_to_pyarray() {
     let slice = matrix.slice(s![1..4; -1, ..]);
     let slice_py = slice.to_pyarray(py);
     assert_eq!(slice_py.as_array(), array![[6, 7], [4, 5], [2, 3]],);
+    pyo3::py_run!(py, slice_py, "assert slice_py.flags['C_CONTIGUOUS']")
+}
+
+#[test]
+fn forder_into_pyarray() {
+    let gil = pyo3::Python::acquire_gil();
+    let py = gil.python();
+    let matrix = Array2::from_shape_vec([4, 2], vec![0, 1, 2, 3, 4, 5, 6, 7]).unwrap();
+    let fortran_matrix = matrix.reversed_axes();
+    let fmat_py = fortran_matrix.into_pyarray(py);
+    assert_eq!(fmat_py.as_array(), array![[0, 2, 4, 6], [1, 3, 5, 7]],);
+    pyo3::py_run!(py, fmat_py, "assert fmat_py.flags['F_CONTIGUOUS']")
 }