Implement *Py* traits for arrays (up to 32)

CHANGELOG.md

@@ -24,6 +24,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 * `FromPyObject` is now automatically implemented for `T: Clone` pyclasses. [#730](https://github.com/PyO3/pyo3/pull/730)
 * `#[pyo3(get)]` and `#[pyo3(set)]` will now use the Rust doc-comment from the field for the Python property. [#755](https://github.com/PyO3/pyo3/pull/755)
 * `#[setter]` functions may now take an argument of `Pyo3::Python`. [#760](https://github.com/PyO3/pyo3/pull/760)
+* Implement `FromPyObject` and `IntoPy<PyObject>` traits for arrays (up to 32). [#778](https://github.com/PyO3/pyo3/pull/778)
 
 ### Fixed
 

src/types/list.rs

@@ -178,6 +178,26 @@ where
     }
 }
 
+macro_rules! array_impls {
+    ($($N:expr),+) => {
+        $(
+            impl<T> IntoPy<PyObject> for [T; $N]
+            where
+                T: ToPyObject
+            {
+                fn into_py(self, py: Python) -> PyObject {
+                    self.as_ref().to_object(py)
+                }
+            }
+        )+
+    }
+}
+
+array_impls!(
+    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
+    26, 27, 28, 29, 30, 31, 32
+);
+
 impl<T> ToPyObject for Vec<T>
 where
     T: ToPyObject,
@@ -209,7 +229,7 @@ mod test {
     use crate::objectprotocol::ObjectProtocol;
     use crate::types::PyList;
     use crate::Python;
-    use crate::{PyTryFrom, ToPyObject};
+    use crate::{PyTryFrom, PyObject, IntoPy, ToPyObject};
 
     #[test]
     fn test_new() {
@@ -423,4 +443,14 @@ mod test {
         assert_eq!(3, list.get_item(2).extract::<i32>().unwrap());
         assert_eq!(2, list.get_item(3).extract::<i32>().unwrap());
     }
+
+    #[test]
+    fn test_array_into_py() {
+        let gil = Python::acquire_gil();
+        let py = gil.python();
+        let array: PyObject = [1, 2].into_py(py);
+        let list = <PyList as PyTryFrom>::try_from(array.as_ref(py)).unwrap();
+        assert_eq!(1, list.get_item(0).extract::<i32>().unwrap());
+        assert_eq!(2, list.get_item(1).extract::<i32>().unwrap());
+    }
 }

src/types/sequence.rs

@@ -2,6 +2,7 @@
 
 use crate::buffer;
 use crate::err::{self, PyDowncastError, PyErr, PyResult};
+use crate::exceptions;
 use crate::ffi::{self, Py_ssize_t};
 use crate::instance::PyNativeType;
 use crate::internal_tricks::Unsendable;
@@ -241,6 +242,48 @@ impl PySequence {
     }
 }
 
+macro_rules! array_impls {
+    ($($N:expr),+) => {
+        $(
+            impl<'a, T> FromPyObject<'a> for [T; $N]
+            where
+                T: Copy + Default + FromPyObject<'a>,
+            {
+                default fn extract(obj: &'a PyAny) -> PyResult<Self> {
+                    let mut array = [T::default(); $N];
+                    extract_sequence_into_slice(obj, &mut array)?;
+                    Ok(array)
+                }
+            }
+
+            impl<'source, T> FromPyObject<'source> for [T; $N]
+            where
+                for<'a> T: Copy + Default + FromPyObject<'a> + buffer::Element,
+            {
+                fn extract(obj: &'source PyAny) -> PyResult<Self> {
+                    let mut array = [T::default(); $N];
+                    // first try buffer protocol
+                    if let Ok(buf) = buffer::PyBuffer::get(obj.py(), obj) {
+                        if buf.dimensions() == 1 && buf.copy_to_slice(obj.py(), &mut array).is_ok() {
+                            buf.release(obj.py());
+                            return Ok(array);
+                        }
+                        buf.release(obj.py());
+                    }
+                    // fall back to sequence protocol
+                    extract_sequence_into_slice(obj, &mut array)?;
+                    Ok(array)
+                }
+            }
+        )+
+    }
+}
+
+array_impls!(
+    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
+    26, 27, 28, 29, 30, 31, 32
+);
+
 impl<'a, T> FromPyObject<'a> for Vec<T>
 where
     T: FromPyObject<'a>,
@@ -282,6 +325,22 @@ where
     Ok(v)
 }
 
+fn extract_sequence_into_slice<'s, T>(obj: &'s PyAny, slice: &mut [T]) -> PyResult<()>
+where
+    T: FromPyObject<'s>,
+{
+    let seq = <PySequence as PyTryFrom>::try_from(obj)?;
+    if seq.len()? as usize != slice.len() {
+        return Err(exceptions::BufferError::py_err(
+            "Slice length does not match buffer length.",
+        ));
+    }
+    for (value, item) in slice.iter_mut().zip(seq.iter()?) {
+        *value = item?.extract::<T>()?;
+    }
+    Ok(())
+}
+
 impl<'v> PyTryFrom<'v> for PySequence {
     fn try_from<V: Into<&'v PyAny>>(value: V) -> Result<&'v PySequence, PyDowncastError> {
         let value = value.into();
@@ -640,6 +699,18 @@ mod test {
         assert!(v == [1, 2, 3, 4]);
     }
 
+    #[test]
+    fn test_extract_bytearray_to_array() {
+        let gil = Python::acquire_gil();
+        let py = gil.python();
+        let v: [u8; 3] = py
+            .eval("bytearray(b'abc')", None, None)
+            .unwrap()
+            .extract()
+            .unwrap();
+        assert!(&v == b"abc");
+    }
+
     #[test]
     fn test_extract_bytearray_to_vec() {
         let gil = Python::acquire_gil();