- Add support for building for CPython limited API. This required a few minor changes to runtime behaviour of of pyo3 `#[pyclass]` types. See the migration guide for full details. [#1152](https://github.com/PyO3/pyo3/pull/1152)
- Change return type `PyType::name()` from `Cow<str>` to `PyResult<&str>`. [#1152](https://github.com/PyO3/pyo3/pull/1152)
-`#[pyclass(subclass)]` is now required for subclassing from Rust (was previously just required for subclassing from Python). [#1152](https://github.com/PyO3/pyo3/pull/1152)
- Change `PyIterator` to be consistent with other native types: it is now used as `&PyIterator` instead of `PyIterator<'a>`. [#1176](https://github.com/PyO3/pyo3/pull/1176)
- Rename `PyTypeInfo::is_instance` and `PyTypeInfo::is_exact_instance` to `PyTypeInfo::is_type_of` and `PyTypeInfo::is_exact_type_of`. [#1278](https://github.com/PyO3/pyo3/pull/1278)
- Optimize `PyAny::call0`, `Py::call0` and `PyAny::call_method0` and `Py::call_method0` on Python 3.9 and up. [#1287](https://github.com/PyO3/pyo3/pull/1285)
- Remove deprecated ffi definitions `PyUnicode_AsUnicodeCopy`, `PyUnicode_GetMax`, `_Py_CheckRecursionLimit`, `PyObject_AsCharBuffer`, `PyObject_AsReadBuffer`, `PyObject_CheckReadBuffer` and `PyObject_AsWriteBuffer`, which will be removed in Python 3.10. [#1217](https://github.com/PyO3/pyo3/pull/1217)
- Fix missing field in `PyCodeObject` struct (`co_posonlyargcount`) - caused invalid access to other fields in Python >3.7. [#1260](https://github.com/PyO3/pyo3/pull/1260)
- Fix building for `x86_64-unknown-linux-musl` target from `x86_65-unknown-linux-gnu` host. [#1267](https://github.com/PyO3/pyo3/pull/1267)
- Fix reference count bug in implementation of `From<Py<T>>` for `PyObject`, a regression introduced in PyO3 0.12. [#1297](https://github.com/PyO3/pyo3/pull/1297)
- Fix support for Rust versions 1.39 to 1.44, broken by an incorrect internal update to paste 1.0 which was done in PyO3 0.12.2. [#1234](https://github.com/PyO3/pyo3/pull/1234)
- Add `PyBytes::new_with` and `PyByteArray::new_with` for initialising `bytes` and `bytearray` objects using a closure. [#1074](https://github.com/PyO3/pyo3/pull/1074)
- Add `Py::as_ref` and `Py::into_ref` for converting `Py<T>` to `&T`. [#1098](https://github.com/PyO3/pyo3/pull/1098)
- Add ability to return `Result` types other than `PyResult` from `#[pyfunction]`, `#[pymethod]` and `#[pyproto]` functions. [#1106](https://github.com/PyO3/pyo3/pull/1118).
- Implement `ToPyObject`, `IntoPy`, and `FromPyObject` for [hashbrown](https://crates.io/crates/hashbrown)'s `HashMap` and `HashSet` types (requires the `hashbrown` feature). [#1114](https://github.com/PyO3/pyo3/pull/1114)
- Add `#[pyfunction(pass_module)]` and `#[pyfn(pass_module)]` to pass the module object as the first function argument. [#1143](https://github.com/PyO3/pyo3/pull/1143)
- Add `PyModule::add_function` and `PyModule::add_submodule` as typed alternatives to `PyModule::add_wrapped`. [#1143](https://github.com/PyO3/pyo3/pull/1143)
- Add native `PyCFunction` and `PyFunction` types. [#1163](https://github.com/PyO3/pyo3/pull/1163)
- Require `T: Send` for the return value `T` of `Python::allow_threads`. [#1036](https://github.com/PyO3/pyo3/pull/1036)
- Rename `PYTHON_SYS_EXECUTABLE` to `PYO3_PYTHON`. The old name will continue to work (undocumented) but will be removed in a future release. [#1039](https://github.com/PyO3/pyo3/pull/1039)
- Remove `unsafe` from signature of `PyType::as_type_ptr`. [#1047](https://github.com/PyO3/pyo3/pull/1047)
- Change return type of `PyIterator::from_object` to `PyResult<PyIterator>` (was `Result<PyIterator, PyDowncastError>`). [#1051](https://github.com/PyO3/pyo3/pull/1051)
- Change `PyObject` to be a type alias for `Py<PyAny>`. [#1063](https://github.com/PyO3/pyo3/pull/1063)
- Rework `PyErr` to be compatible with the `std::error::Error` trait: [#1067](https://github.com/PyO3/pyo3/pull/1067) [#1115](https://github.com/PyO3/pyo3/pull/1115)
-`PyErr`'s fields are now an implementation detail. The equivalent values can be accessed with `PyErr::ptype()`, `PyErr::pvalue()` and `PyErr::ptraceback()`.
- Remove `Into<PyResult<T>>` for `PyErr` and `PyException`.
- Change methods generated by `#[pyproto]` to return `NotImplemented` if Python should try a reversed operation. #[1072](https://github.com/PyO3/pyo3/pull/1072)
- Change argument to `PyModule::add` to `impl IntoPy<PyObject>` (was `impl ToPyObject`). #[1124](https://github.com/PyO3/pyo3/pull/1124)
- Remove many exception and `PyErr` APIs; see the "changed" section above. [#1024](https://github.com/PyO3/pyo3/pull/1024) [#1067](https://github.com/PyO3/pyo3/pull/1067) [#1115](https://github.com/PyO3/pyo3/pull/1115)
- Remove `PyString::to_string` (use new `PyString::to_str`). [#1023](https://github.com/PyO3/pyo3/pull/1023)
- Correct FFI definitions `Py_SetProgramName` and `Py_SetPythonHome` to take `*const` arguments (was `*mut`). [#1021](https://github.com/PyO3/pyo3/pull/1021)
- Fix `FromPyObject` for `num_bigint::BigInt` for Python objects with an `__index__` method. [#1027](https://github.com/PyO3/pyo3/pull/1027)
- Correct FFI definition `_PyLong_AsByteArray` to take `*mut c_uchar` argument (was `*const c_uchar`). [#1029](https://github.com/PyO3/pyo3/pull/1029)
- Fix segfault with `#[pyclass(dict, unsendable)]`. [#1058](https://github.com/PyO3/pyo3/pull/1058) [#1059](https://github.com/PyO3/pyo3/pull/1059)
- Fix using `&Self` as an argument type for functions in a `#[pymethods]` block. [#1071](https://github.com/PyO3/pyo3/pull/1071)
- Fix best-effort build against PyPy 3.6. [#1092](https://github.com/PyO3/pyo3/pull/1092)
- Fix many cases of lifetime elision in `#[pyproto]` implementations. [#1093](https://github.com/PyO3/pyo3/pull/1093)
- Fix detection of Python build configuration when cross-compiling. [#1095](https://github.com/PyO3/pyo3/pull/1095)
- Always link against libpython on android with the `extension-module` feature. [#1095](https://github.com/PyO3/pyo3/pull/1095)
- Fix the `+` operator not trying `__radd__` when both `__add__` and `__radd__` are defined in `PyNumberProtocol` (and similar for all other reversible operators). [#1107](https://github.com/PyO3/pyo3/pull/1107)
- Fix building with Anaconda python. [#1175](https://github.com/PyO3/pyo3/pull/1175)
-`#[pyproto]` methods can now have return value `T` or `PyResult<T>` (previously only `PyResult<T>` was supported). [#996](https://github.com/PyO3/pyo3/pull/996)
- Panics will now be raised as a Python `PanicException`. [#797](https://github.com/PyO3/pyo3/pull/797)
- Change `PyObject` and `Py<T>` reference counts to decrement immediately upon drop when the GIL is held. [#851](https://github.com/PyO3/pyo3/pull/851)
- Allow `PyIterProtocol` methods to use either `PyRef` or `PyRefMut` as the receiver type. [#856](https://github.com/PyO3/pyo3/pull/856)
- Change the implementation of `FromPyObject` for `Py<T>` to apply to a wider range of `T`, including all `T: PyClass`. [#880](https://github.com/PyO3/pyo3/pull/880)
- Move all methods from the `ObjectProtocol` trait to the `PyAny` struct. [#911](https://github.com/PyO3/pyo3/pull/911)
- Remove need for `#![feature(specialization)]` in crates depending on PyO3. [#917](https://github.com/PyO3/pyo3/pull/917)
- Fix support for `__radd__` and other `__r*__` methods as implementations for Python mathematical operators. [#839](https://github.com/PyO3/pyo3/pull/839)
- Fix panics during garbage collection when traversing objects that were already mutably borrowed. [#855](https://github.com/PyO3/pyo3/pull/855)
- Prevent `&'static` references to Python objects as arguments to `#[pyfunction]` and `#[pymethods]`. [#869](https://github.com/PyO3/pyo3/pull/869)
- Fix lifetime safety bug with `AsPyRef::as_ref`. [#876](https://github.com/PyO3/pyo3/pull/876)
- Fix `#[pyo3(get)]` attribute on `Py<T>` fields. [#880](https://github.com/PyO3/pyo3/pull/880)
- Fix segmentation faults caused by functions such as `PyList::get_item` returning borrowed objects when it was not safe to do so. [#890](https://github.com/PyO3/pyo3/pull/890)
- 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)]`
