- Methods and associated constants can now be annotated with `#[classattr]` to define class attributes. [#905](https://github.com/PyO3/pyo3/pull/905) [#914](https://github.com/PyO3/pyo3/pull/914)
- Panics from Rust will now be caught and raised as Python errors. [#797](https://github.com/PyO3/pyo3/pull/797)
-`PyObject` and `Py<T>` reference counts are now decremented sooner after `drop()`. [#851](https://github.com/PyO3/pyo3/pull/851)
- When the GIL is held, the refcount is now decreased immediately on drop. (Previously would wait until just before releasing the GIL.)
- When the GIL is not held, the refcount is now decreased when the GIL is next acquired. (Previously would wait until next time the GIL was released.)
-`FromPyObject` for `Py<T>` now works for a wider range of `T`, in particular for `T: PyClass`. [#880](https://github.com/PyO3/pyo3/pull/880)
- Some functions such as `PyList::get_item` which return borrowed objects at the C ffi layer now return owned objects at the PyO3 layer, for safety reasons. [#890](https://github.com/PyO3/pyo3/pull/890)
- The `GILGuard` returned from `Python::acquire_gil` will now only assume responsiblity for freeing owned references on drop if no other `GILPool` or `GILGuard` exists. This ensures that multiple calls to the safe api `Python::acquire_gil` cannot lead to dangling references. [#893](https://github.com/PyO3/pyo3/pull/893)
- The trait `ObjectProtocol` has been removed, and all the methods from the trait have been moved to `PyAny`. [#911](https://github.com/PyO3/pyo3/pull/911)
- The exception to this is `ObjectProtocol::None`, which has simply been removed. Use `Python::None` instead.
- Implemented `IntoIterator` for `PySet` and `PyFrozenSet`. [#716](https://github.com/PyO3/pyo3/pull/716)
-`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)
-`PyTypeInfo::BaseLayout` and `PyClass::BaseNativeType`. [#770](https://github.com/PyO3/pyo3/pull/770)
-`#[new]` does not take `PyRawObject` and can return `Self`. [#683](https://github.com/PyO3/pyo3/pull/683)
- The blanket implementations for `FromPyObject` for `&T` and `&mut T` are no longer specializable. Implement `PyTryFrom` for your type to control the behavior of `FromPyObject::extract()` for your types. [#713](https://github.com/PyO3/pyo3/pull/713)
- The implementation for `IntoPy<U> for T` where `U: FromPy<T>` is no longer specializable. Control the behavior of this via the implementation of `FromPy`. [#713](https://github.com/PyO3/pyo3/pull/713)
- Use `parking_lot::Mutex` instead of `spin::Mutex`. [#734](https://github.com/PyO3/pyo3/pull/734)
- Bumped minimum Rust version to `1.42.0-nightly 2020-01-21`. [#761](https://github.com/PyO3/pyo3/pull/761)
-`PyRef` and `PyRefMut` are renewed for `PyCell`. [#770](https://github.com/PyO3/pyo3/pull/770)
- Some new FFI functions for Python 3.8. [#784](https://github.com/PyO3/pyo3/pull/784)
-`PyAny` is now on the top level module and prelude. [#816](https://github.com/PyO3/pyo3/pull/816)
- Fixed unsoundness of subclassing. [#683](https://github.com/PyO3/pyo3/pull/683).
- Clear error indicator when the exception is handled on the Rust side. [#719](https://github.com/PyO3/pyo3/pull/719)
- Usage of raw identifiers with `#[pyo3(set)]`. [#745](https://github.com/PyO3/pyo3/pull/745)
- Usage of `PyObject` with `#[pyo3(get)]`. [#760](https://github.com/PyO3/pyo3/pull/760)
-`#[pymethods]` used in conjunction with `#[cfg]`. #[769](https://github.com/PyO3/pyo3/pull/769)
-`"*"` in a `#[pyfunction()]` argument list incorrectly accepting any number of positional arguments (use `args = "*"` when this behaviour is desired). #[792](https://github.com/PyO3/pyo3/pull/792)
- Implementing the Using the `gc` parameter for `pyclass` (e.g. `#[pyclass(gc)]`) without implementing the `class::PyGCProtocol` trait is now a compile-time error. Failing to implement this trait could lead to segfaults. [#532](https://github.com/PyO3/pyo3/pull/532)
-`PyByteArray::data` has been replaced with `PyDataArray::to_vec` because returning a `&[u8]` is unsound. (See [this comment](https://github.com/PyO3/pyo3/issues/373#issuecomment-512332696) for a great write-up for why that was unsound)
- Replace `mashup` with `paste`.
-`GILPool` gained a `Python` marker to prevent it from being misused to release Python objects without the GIL held.
- Currently, [#341](https://github.com/PyO3/pyo3/issues/341) causes `cargo test` to fail with weird linking errors when the `extension-module` feature is activated. For now you can work around this by making the `extension-module` feature optional and running the tests with `cargo test --no-default-features`:
- Added a `wrap_pymodule!` macro similar to the existing `wrap_pyfunction!` macro. Only available on python 3
- Added support for cross compiling (e.g. to arm v7) by mtp401 in [#327](https://github.com/PyO3/pyo3/pull/327). See the "Cross Compiling" section in the "Building and Distribution" chapter of the guide for more details.
- The `PyRef` and `PyRefMut` types, which allow to differentiate between an instance of a rust struct on the rust heap and an instance that is embedded inside a python object. By kngwyu in [#335](https://github.com/PyO3/pyo3/pull/335)
- Added `FromPy<T>` and `IntoPy<T>` which are equivalent to `From<T>` and `Into<T>` except that they require a gil token.
- Added `ManagedPyRef`, which should eventually replace `ToBorrowedObject`.
- A soudness hole where every instances of a `#[pyclass]` struct was considered to be part of a python object, even though you can create instances that are not part of the python heap. This was fixed through `PyRef` and `PyRefMut`.
- Fix kwargs support in [#328](https://github.com/PyO3/pyo3/pull/328).
- Add full support for `__dict__` in [#403](https://github.com/PyO3/pyo3/pull/403).
-`#[pyclass]` objects can now be returned from rust functions
-`PyComplex` by kngwyu in [#226](https://github.com/PyO3/pyo3/pull/226)
-`PyDict::from_sequence()`, equivalent to `dict([(key, val), ...])`
- Bindings for the `datetime` standard library types: `PyDate`, `PyTime`, `PyDateTime`, `PyTzInfo`, `PyDelta` with associated `ffi` types, by pganssle [#200](https://github.com/PyO3/pyo3/pull/200).
-`PyString`, `PyUnicode`, and `PyBytes` now have an `as_bytes()` method that returns `&[u8]`.
-`PyObjectProtocol::get_type_ptr()` by ijl in [#242](https://github.com/PyO3/pyo3/pull/242)
- Upgraded to syn 0.14 which means much better error messages :tada:
- 128 bit integer support by [kngwyu](https://github.com/kngwyu) ([#137](https://github.com/PyO3/pyo3/pull/173))
-`proc_macro` has been stabilized on nightly ([rust-lang/rust#52081](https://github.com/rust-lang/rust/pull/52081)). This means that we can remove the `proc_macro` feature, but now we need the `use_extern_macros` from the 2018 edition instead.
- All proc macro are now prefixed with `py` and live in the prelude. This means you can use `#[pyclass]`, `#[pymethods]`, `#[pyproto]`, `#[pyfunction]` and `#[pymodinit]` directly, at least after a `use pyo3::prelude::*`. They were also moved into a module called `proc_macro`. You shouldn't use `#[pyo3::proc_macro::pyclass]` or other longer paths in attributes because `proc_macro_path_invoc` isn't going to be stabilized soon.
- Renamed the `base` option in the `pyclass` macro to `extends`.
-`#[pymodinit]` uses the function name as module name, unless the name is overrriden with `#[pymodinit(name)]`
