/
instance.rs
2256 lines (2077 loc) · 71 KB
/
instance.rs
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use crate::err::{self, PyDowncastError, PyErr, PyResult};
use crate::ffi_ptr_ext::FfiPtrExt;
use crate::pycell::{PyBorrowError, PyBorrowMutError, PyCell};
use crate::pyclass::boolean_struct::{False, True};
use crate::type_object::HasPyGilRef;
use crate::types::{any::PyAnyMethods, string::PyStringMethods, typeobject::PyTypeMethods};
use crate::types::{PyDict, PyString, PyTuple};
use crate::{
ffi, AsPyPointer, DowncastError, FromPyObject, IntoPy, PyAny, PyClass, PyClassInitializer,
PyRef, PyRefMut, PyTypeInfo, Python, ToPyObject,
};
use crate::{gil, PyTypeCheck};
use std::marker::PhantomData;
use std::mem::ManuallyDrop;
use std::ops::Deref;
use std::ptr::NonNull;
/// Types that are built into the Python interpreter.
///
/// PyO3 is designed in a way that all references to those types are bound
/// to the GIL, which is why you can get a token from all references of those
/// types.
///
/// # Safety
///
/// This trait must only be implemented for types which cannot be accessed without the GIL.
pub unsafe trait PyNativeType: Sized {
/// The form of this which is stored inside a `Py<T>` smart pointer.
type AsRefSource: HasPyGilRef<AsRefTarget = Self>;
/// Cast `&self` to a `Borrowed` smart pointer.
///
/// `Borrowed<T>` implements `Deref<Target=Bound<T>>`, so can also be used in locations
/// where `Bound<T>` is expected.
///
/// This is available as a migration tool to adjust code from the deprecated "GIL Refs"
/// API to the `Bound` smart pointer API.
#[inline]
fn as_borrowed(&self) -> Borrowed<'_, '_, Self::AsRefSource> {
// Safety: &'py Self is expected to be a Python pointer,
// so has the same layout as Borrowed<'py, 'py, T>
Borrowed(
unsafe { NonNull::new_unchecked(self as *const Self as *mut _) },
PhantomData,
self.py(),
)
}
/// Returns a GIL marker constrained to the lifetime of this type.
#[inline]
fn py(&self) -> Python<'_> {
unsafe { Python::assume_gil_acquired() }
}
/// Cast `&PyAny` to `&Self` without no type checking.
///
/// # Safety
///
/// `obj` must have the same layout as `*const ffi::PyObject` and must be
/// an instance of a type corresponding to `Self`.
unsafe fn unchecked_downcast(obj: &PyAny) -> &Self {
&*(obj.as_ptr() as *const Self)
}
}
/// A GIL-attached equivalent to `Py`.
#[repr(transparent)]
pub struct Bound<'py, T>(Python<'py>, ManuallyDrop<Py<T>>);
impl<'py, T> Bound<'py, T>
where
T: PyClass,
{
/// Creates a new instance `Bound<T>` of a `#[pyclass]` on the Python heap.
///
/// # Examples
///
/// ```rust
/// use pyo3::prelude::*;
///
/// #[pyclass]
/// struct Foo {/* fields omitted */}
///
/// # fn main() -> PyResult<()> {
/// Python::with_gil(|py| -> PyResult<Py<Foo>> {
/// let foo: Bound<'_, Foo> = Bound::new(py, Foo {})?;
/// Ok(foo.into())
/// })?;
/// # Ok(())
/// # }
/// ```
pub fn new(
py: Python<'py>,
value: impl Into<PyClassInitializer<T>>,
) -> PyResult<Bound<'py, T>> {
let initializer = value.into();
let obj = initializer.create_cell(py)?;
let ob = unsafe {
obj.cast::<ffi::PyObject>()
.assume_owned(py)
.downcast_into_unchecked()
};
Ok(ob)
}
}
impl<'py> Bound<'py, PyAny> {
/// Constructs a new `Bound<'py, PyAny>` from a pointer. Panics if `ptr` is null.
///
/// # Safety
///
/// - `ptr` must be a valid pointer to a Python object
/// - `ptr` must be an owned Python reference, as the `Bound<'py, PyAny>` will assume ownership
pub unsafe fn from_owned_ptr(py: Python<'py>, ptr: *mut ffi::PyObject) -> Self {
Self(py, ManuallyDrop::new(Py::from_owned_ptr(py, ptr)))
}
/// Constructs a new `Bound<'py, PyAny>` from a pointer. Returns `None` if `ptr` is null.
///
/// # Safety
///
/// - `ptr` must be a valid pointer to a Python object, or null
/// - `ptr` must be an owned Python reference, as the `Bound<'py, PyAny>` will assume ownership
pub unsafe fn from_owned_ptr_or_opt(py: Python<'py>, ptr: *mut ffi::PyObject) -> Option<Self> {
Py::from_owned_ptr_or_opt(py, ptr).map(|obj| Self(py, ManuallyDrop::new(obj)))
}
/// Constructs a new `Bound<'py, PyAny>` from a pointer. Returns an `Err` by calling `PyErr::fetch`
/// if `ptr` is null.
///
/// # Safety
///
/// - `ptr` must be a valid pointer to a Python object, or null
/// - `ptr` must be an owned Python reference, as the `Bound<'py, PyAny>` will assume ownership
pub unsafe fn from_owned_ptr_or_err(
py: Python<'py>,
ptr: *mut ffi::PyObject,
) -> PyResult<Self> {
Py::from_owned_ptr_or_err(py, ptr).map(|obj| Self(py, ManuallyDrop::new(obj)))
}
/// Constructs a new `Bound<'py, PyAny>` from a pointer by creating a new Python reference.
/// Panics if `ptr` is null.
///
/// # Safety
///
/// - `ptr` must be a valid pointer to a Python object
pub unsafe fn from_borrowed_ptr(py: Python<'py>, ptr: *mut ffi::PyObject) -> Self {
Self(py, ManuallyDrop::new(Py::from_borrowed_ptr(py, ptr)))
}
/// Constructs a new `Bound<'py, PyAny>` from a pointer by creating a new Python reference.
/// Returns `None` if `ptr` is null.
///
/// # Safety
///
/// - `ptr` must be a valid pointer to a Python object, or null
pub unsafe fn from_borrowed_ptr_or_opt(
py: Python<'py>,
ptr: *mut ffi::PyObject,
) -> Option<Self> {
Py::from_borrowed_ptr_or_opt(py, ptr).map(|obj| Self(py, ManuallyDrop::new(obj)))
}
/// Constructs a new `Bound<'py, PyAny>` from a pointer by creating a new Python reference.
/// Returns an `Err` by calling `PyErr::fetch` if `ptr` is null.
///
/// # Safety
///
/// - `ptr` must be a valid pointer to a Python object, or null
pub unsafe fn from_borrowed_ptr_or_err(
py: Python<'py>,
ptr: *mut ffi::PyObject,
) -> PyResult<Self> {
Py::from_borrowed_ptr_or_err(py, ptr).map(|obj| Self(py, ManuallyDrop::new(obj)))
}
/// This slightly strange method is used to obtain `&Bound<PyAny>` from a pointer in macro code
/// where we need to constrain the lifetime `'a` safely.
///
/// Note that `'py` is required to outlive `'a` implicitly by the nature of the fact that
/// `&'a Bound<'py>` means that `Bound<'py>` exists for at least the lifetime `'a`.
///
/// # Safety
/// - `ptr` must be a valid pointer to a Python object for the lifetime `'a`. The `ptr` can
/// be either a borrowed reference or an owned reference, it does not matter, as this is
/// just `&Bound` there will never be any ownership transfer.
#[inline]
pub(crate) unsafe fn ref_from_ptr<'a>(
_py: Python<'py>,
ptr: &'a *mut ffi::PyObject,
) -> &'a Self {
&*(ptr as *const *mut ffi::PyObject).cast::<Bound<'py, PyAny>>()
}
}
impl<'py, T> Bound<'py, T>
where
T: PyClass,
{
/// Immutably borrows the value `T`.
///
/// This borrow lasts while the returned [`PyRef`] exists.
/// Multiple immutable borrows can be taken out at the same time.
///
/// For frozen classes, the simpler [`get`][Self::get] is available.
///
/// # Examples
///
/// ```rust
/// # use pyo3::prelude::*;
/// #
/// #[pyclass]
/// struct Foo {
/// inner: u8,
/// }
///
/// # fn main() -> PyResult<()> {
/// Python::with_gil(|py| -> PyResult<()> {
/// let foo: Bound<'_, Foo> = Bound::new(py, Foo { inner: 73 })?;
/// let inner: &u8 = &foo.borrow().inner;
///
/// assert_eq!(*inner, 73);
/// Ok(())
/// })?;
/// # Ok(())
/// # }
/// ```
///
/// # Panics
///
/// Panics if the value is currently mutably borrowed. For a non-panicking variant, use
/// [`try_borrow`](#method.try_borrow).
pub fn borrow(&'py self) -> PyRef<'py, T> {
self.get_cell().borrow()
}
/// Mutably borrows the value `T`.
///
/// This borrow lasts while the returned [`PyRefMut`] exists.
///
/// # Examples
///
/// ```
/// # use pyo3::prelude::*;
/// #
/// #[pyclass]
/// struct Foo {
/// inner: u8,
/// }
///
/// # fn main() -> PyResult<()> {
/// Python::with_gil(|py| -> PyResult<()> {
/// let foo: Bound<'_, Foo> = Bound::new(py, Foo { inner: 73 })?;
/// foo.borrow_mut().inner = 35;
///
/// assert_eq!(foo.borrow().inner, 35);
/// Ok(())
/// })?;
/// # Ok(())
/// # }
/// ```
///
/// # Panics
/// Panics if the value is currently borrowed. For a non-panicking variant, use
/// [`try_borrow_mut`](#method.try_borrow_mut).
pub fn borrow_mut(&'py self) -> PyRefMut<'py, T>
where
T: PyClass<Frozen = False>,
{
self.get_cell().borrow_mut()
}
/// Attempts to immutably borrow the value `T`, returning an error if the value is currently mutably borrowed.
///
/// The borrow lasts while the returned [`PyRef`] exists.
///
/// This is the non-panicking variant of [`borrow`](#method.borrow).
///
/// For frozen classes, the simpler [`get`][Self::get] is available.
pub fn try_borrow(&'py self) -> Result<PyRef<'py, T>, PyBorrowError> {
self.get_cell().try_borrow()
}
/// Attempts to mutably borrow the value `T`, returning an error if the value is currently borrowed.
///
/// The borrow lasts while the returned [`PyRefMut`] exists.
///
/// This is the non-panicking variant of [`borrow_mut`](#method.borrow_mut).
pub fn try_borrow_mut(&'py self) -> Result<PyRefMut<'py, T>, PyBorrowMutError>
where
T: PyClass<Frozen = False>,
{
self.get_cell().try_borrow_mut()
}
/// Provide an immutable borrow of the value `T` without acquiring the GIL.
///
/// This is available if the class is [`frozen`][macro@crate::pyclass] and [`Sync`].
///
/// # Examples
///
/// ```
/// use std::sync::atomic::{AtomicUsize, Ordering};
/// # use pyo3::prelude::*;
///
/// #[pyclass(frozen)]
/// struct FrozenCounter {
/// value: AtomicUsize,
/// }
///
/// Python::with_gil(|py| {
/// let counter = FrozenCounter { value: AtomicUsize::new(0) };
///
/// let py_counter = Bound::new(py, counter).unwrap();
///
/// py_counter.get().value.fetch_add(1, Ordering::Relaxed);
/// });
/// ```
pub fn get(&self) -> &T
where
T: PyClass<Frozen = True> + Sync,
{
let cell = self.get_cell();
// SAFETY: The class itself is frozen and `Sync` and we do not access anything but `cell.contents.value`.
unsafe { &*cell.get_ptr() }
}
fn get_cell(&'py self) -> &'py PyCell<T> {
let cell = self.as_ptr().cast::<PyCell<T>>();
// SAFETY: Bound<T> is known to contain an object which is laid out in memory as a
// PyCell<T>.
//
// Strictly speaking for now `&'py PyCell<T>` is part of the "GIL Ref" API, so this
// could use some further refactoring later to avoid going through this reference.
unsafe { &*cell }
}
}
impl<'py, T> std::fmt::Debug for Bound<'py, T> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
let any = self.as_any();
python_format(any, any.repr(), f)
}
}
impl<'py, T> std::fmt::Display for Bound<'py, T> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
let any = self.as_any();
python_format(any, any.str(), f)
}
}
fn python_format(
any: &Bound<'_, PyAny>,
format_result: PyResult<Bound<'_, PyString>>,
f: &mut std::fmt::Formatter<'_>,
) -> Result<(), std::fmt::Error> {
match format_result {
Result::Ok(s) => return f.write_str(&s.to_string_lossy()),
Result::Err(err) => err.write_unraisable_bound(any.py(), Some(any)),
}
match any.get_type().name() {
Result::Ok(name) => std::write!(f, "<unprintable {} object>", name),
Result::Err(_err) => f.write_str("<unprintable object>"),
}
}
impl<'py, T> Deref for Bound<'py, T>
where
T: AsRef<PyAny>,
{
type Target = Bound<'py, PyAny>;
#[inline]
fn deref(&self) -> &Bound<'py, PyAny> {
self.as_any()
}
}
impl<'py, T> AsRef<Bound<'py, PyAny>> for Bound<'py, T>
where
T: AsRef<PyAny>,
{
#[inline]
fn as_ref(&self) -> &Bound<'py, PyAny> {
self.as_any()
}
}
impl<T> Clone for Bound<'_, T> {
#[inline]
fn clone(&self) -> Self {
Self(self.0, ManuallyDrop::new(self.1.clone_ref(self.0)))
}
}
impl<T> Drop for Bound<'_, T> {
#[inline]
fn drop(&mut self) {
unsafe { ffi::Py_DECREF(self.as_ptr()) }
}
}
impl<'py, T> Bound<'py, T> {
/// Returns the GIL token associated with this object.
#[inline]
pub fn py(&self) -> Python<'py> {
self.0
}
/// Returns the raw FFI pointer represented by self.
///
/// # Safety
///
/// Callers are responsible for ensuring that the pointer does not outlive self.
///
/// The reference is borrowed; callers should not decrease the reference count
/// when they are finished with the pointer.
#[inline]
pub fn as_ptr(&self) -> *mut ffi::PyObject {
self.1.as_ptr()
}
/// Returns an owned raw FFI pointer represented by self.
///
/// # Safety
///
/// The reference is owned; when finished the caller should either transfer ownership
/// of the pointer or decrease the reference count (e.g. with [`pyo3::ffi::Py_DecRef`](crate::ffi::Py_DecRef)).
#[inline]
pub fn into_ptr(self) -> *mut ffi::PyObject {
ManuallyDrop::new(self).as_ptr()
}
/// Helper to cast to `Bound<'py, PyAny>`.
#[inline]
pub fn as_any(&self) -> &Bound<'py, PyAny> {
// Safety: all Bound<T> have the same memory layout, and all Bound<T> are valid
// Bound<PyAny>, so pointer casting is valid.
unsafe { &*(self as *const Self).cast::<Bound<'py, PyAny>>() }
}
/// Helper to cast to `Bound<'py, PyAny>`, transferring ownership.
#[inline]
pub fn into_any(self) -> Bound<'py, PyAny> {
// Safety: all Bound<T> are valid Bound<PyAny>
Bound(self.0, ManuallyDrop::new(self.unbind().into_any()))
}
/// Casts this `Bound<T>` to a `Borrowed<T>` smart pointer.
#[inline]
pub fn as_borrowed<'a>(&'a self) -> Borrowed<'a, 'py, T> {
Borrowed(
unsafe { NonNull::new_unchecked(self.as_ptr()) },
PhantomData,
self.py(),
)
}
/// Removes the connection for this `Bound<T>` from the GIL, allowing
/// it to cross thread boundaries.
#[inline]
pub fn unbind(self) -> Py<T> {
// Safety: the type T is known to be correct and the ownership of the
// pointer is transferred to the new Py<T> instance.
let non_null = (ManuallyDrop::new(self).1).0;
unsafe { Py::from_non_null(non_null) }
}
/// Casts this `Bound<T>` as the corresponding "GIL Ref" type.
///
/// This is a helper to be used for migration from the deprecated "GIL Refs" API.
#[inline]
pub fn as_gil_ref(&'py self) -> &'py T::AsRefTarget
where
T: HasPyGilRef,
{
unsafe { self.py().from_borrowed_ptr(self.as_ptr()) }
}
/// Casts this `Bound<T>` as the corresponding "GIL Ref" type, registering the pointer on the
/// [release pool](Python::from_owned_ptr).
///
/// This is a helper to be used for migration from the deprecated "GIL Refs" API.
#[inline]
pub fn into_gil_ref(self) -> &'py T::AsRefTarget
where
T: HasPyGilRef,
{
unsafe { self.py().from_owned_ptr(self.into_ptr()) }
}
}
unsafe impl<T> AsPyPointer for Bound<'_, T> {
fn as_ptr(&self) -> *mut ffi::PyObject {
self.1.as_ptr()
}
}
/// A borrowed equivalent to `Bound`.
///
/// The advantage of this over `&Bound` is that it avoids the need to have a pointer-to-pointer, as Bound
/// is already a pointer to an `ffi::PyObject``.
///
/// Similarly, this type is `Copy` and `Clone`, like a shared reference (`&T`).
#[repr(transparent)]
pub struct Borrowed<'a, 'py, T>(NonNull<ffi::PyObject>, PhantomData<&'a Py<T>>, Python<'py>);
impl<'py, T> Borrowed<'_, 'py, T> {
/// Creates a new owned `Bound` from this borrowed reference by increasing the reference count.
pub(crate) fn to_owned(self) -> Bound<'py, T> {
(*self).clone()
}
}
impl<'a, 'py> Borrowed<'a, 'py, PyAny> {
/// Constructs a new `Borrowed<'a, 'py, PyAny>` from a pointer. Panics if `ptr` is null.
///
/// Prefer to use [`Bound::from_borrowed_ptr`], as that avoids the major safety risk
/// of needing to precisely define the lifetime `'a` for which the borrow is valid.
///
/// # Safety
///
/// - `ptr` must be a valid pointer to a Python object
/// - similar to `std::slice::from_raw_parts`, the lifetime `'a` is completely defined by
/// the caller and it is the caller's responsibility to ensure that the reference this is
/// derived from is valid for the lifetime `'a`.
pub unsafe fn from_ptr(py: Python<'py>, ptr: *mut ffi::PyObject) -> Self {
Self(
NonNull::new(ptr).unwrap_or_else(|| crate::err::panic_after_error(py)),
PhantomData,
py,
)
}
/// Constructs a new `Borrowed<'a, 'py, PyAny>` from a pointer. Returns `None` if `ptr` is null.
///
/// Prefer to use [`Bound::from_borrowed_ptr_or_opt`], as that avoids the major safety risk
/// of needing to precisely define the lifetime `'a` for which the borrow is valid.
///
/// # Safety
///
/// - `ptr` must be a valid pointer to a Python object, or null
/// - similar to `std::slice::from_raw_parts`, the lifetime `'a` is completely defined by
/// the caller and it is the caller's responsibility to ensure that the reference this is
/// derived from is valid for the lifetime `'a`.
pub unsafe fn from_ptr_or_opt(py: Python<'py>, ptr: *mut ffi::PyObject) -> Option<Self> {
NonNull::new(ptr).map(|ptr| Self(ptr, PhantomData, py))
}
/// Constructs a new `Borrowed<'a, 'py, PyAny>` from a pointer. Returns an `Err` by calling `PyErr::fetch`
/// if `ptr` is null.
///
/// Prefer to use [`Bound::from_borrowed_ptr_or_err`], as that avoids the major safety risk
/// of needing to precisely define the lifetime `'a` for which the borrow is valid.
///
/// # Safety
///
/// - `ptr` must be a valid pointer to a Python object, or null
/// - similar to `std::slice::from_raw_parts`, the lifetime `'a` is completely defined by
/// the caller and it is the caller's responsibility to ensure that the reference this is
/// derived from is valid for the lifetime `'a`.
pub unsafe fn from_ptr_or_err(py: Python<'py>, ptr: *mut ffi::PyObject) -> PyResult<Self> {
NonNull::new(ptr).map_or_else(
|| Err(PyErr::fetch(py)),
|ptr| Ok(Self(ptr, PhantomData, py)),
)
}
/// # Safety
/// This is similar to `std::slice::from_raw_parts`, the lifetime `'a` is completely defined by
/// the caller and it's the caller's responsibility to ensure that the reference this is
/// derived from is valid for the lifetime `'a`.
pub(crate) unsafe fn from_ptr_unchecked(py: Python<'py>, ptr: *mut ffi::PyObject) -> Self {
Self(NonNull::new_unchecked(ptr), PhantomData, py)
}
/// Converts this `PyAny` to a concrete Python type without checking validity.
///
/// # Safety
/// Callers must ensure that the type is valid or risk type confusion.
pub(crate) unsafe fn downcast_unchecked<T>(self) -> Borrowed<'a, 'py, T> {
Borrowed(self.0, PhantomData, self.2)
}
}
impl<'a, 'py, T> From<&'a Bound<'py, T>> for Borrowed<'a, 'py, T> {
/// Create borrow on a Bound
fn from(instance: &'a Bound<'py, T>) -> Self {
instance.as_borrowed()
}
}
impl<'py, T> Borrowed<'py, 'py, T>
where
T: HasPyGilRef,
{
pub(crate) fn into_gil_ref(self) -> &'py T::AsRefTarget {
// Safety: self is a borrow over `'py`.
unsafe { self.py().from_borrowed_ptr(self.0.as_ptr()) }
}
}
impl<T> std::fmt::Debug for Borrowed<'_, '_, T> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
Bound::fmt(self, f)
}
}
impl<'py, T> Deref for Borrowed<'_, 'py, T> {
type Target = Bound<'py, T>;
#[inline]
fn deref(&self) -> &Bound<'py, T> {
// safety: Bound has the same layout as NonNull<ffi::PyObject>
unsafe { &*(&self.0 as *const _ as *const Bound<'py, T>) }
}
}
impl<T> Clone for Borrowed<'_, '_, T> {
#[inline]
fn clone(&self) -> Self {
*self
}
}
impl<T> Copy for Borrowed<'_, '_, T> {}
impl<T> ToPyObject for Borrowed<'_, '_, T> {
/// Converts `Py` instance -> PyObject.
#[inline]
fn to_object(&self, py: Python<'_>) -> PyObject {
(*self).into_py(py)
}
}
impl<T> IntoPy<PyObject> for Borrowed<'_, '_, T> {
/// Converts `Py` instance -> PyObject.
#[inline]
fn into_py(self, py: Python<'_>) -> PyObject {
self.to_owned().into_py(py)
}
}
/// A GIL-independent reference to an object allocated on the Python heap.
///
/// This type does not auto-dereference to the inner object because you must prove you hold the GIL to access it.
/// Instead, call one of its methods to access the inner object:
/// - [`Py::as_ref`], to borrow a GIL-bound reference to the contained object.
/// - [`Py::borrow`], [`Py::try_borrow`], [`Py::borrow_mut`], or [`Py::try_borrow_mut`],
/// to get a (mutable) reference to a contained pyclass, using a scheme similar to std's [`RefCell`].
/// See the [`PyCell` guide entry](https://pyo3.rs/latest/class.html#pycell-and-interior-mutability)
/// for more information.
/// - You can call methods directly on `Py` with [`Py::call`], [`Py::call_method`] and friends.
/// These require passing in the [`Python<'py>`](crate::Python) token but are otherwise similar to the corresponding
/// methods on [`PyAny`].
///
/// # Example: Storing Python objects in structs
///
/// As all the native Python objects only appear as references, storing them in structs doesn't work well.
/// For example, this won't compile:
///
/// ```compile_fail
/// # use pyo3::prelude::*;
/// # use pyo3::types::PyDict;
/// #
/// #[pyclass]
/// struct Foo<'py> {
/// inner: &'py PyDict,
/// }
///
/// impl Foo {
/// fn new() -> Foo {
/// let foo = Python::with_gil(|py| {
/// // `py` will only last for this scope.
///
/// // `&PyDict` derives its lifetime from `py` and
/// // so won't be able to outlive this closure.
/// let dict: &PyDict = PyDict::new(py);
///
/// // because `Foo` contains `dict` its lifetime
/// // is now also tied to `py`.
/// Foo { inner: dict }
/// });
/// // Foo is no longer valid.
/// // Returning it from this function is a 💥 compiler error 💥
/// foo
/// }
/// }
/// ```
///
/// [`Py`]`<T>` can be used to get around this by converting `dict` into a GIL-independent reference:
///
/// ```rust
/// use pyo3::prelude::*;
/// use pyo3::types::PyDict;
///
/// #[pyclass]
/// struct Foo {
/// inner: Py<PyDict>,
/// }
///
/// #[pymethods]
/// impl Foo {
/// #[new]
/// fn __new__() -> Foo {
/// Python::with_gil(|py| {
/// let dict: Py<PyDict> = PyDict::new_bound(py).unbind();
/// Foo { inner: dict }
/// })
/// }
/// }
/// #
/// # fn main() -> PyResult<()> {
/// # Python::with_gil(|py| {
/// # let m = pyo3::types::PyModule::new(py, "test")?;
/// # m.add_class::<Foo>()?;
/// #
/// # let foo: &PyCell<Foo> = m.getattr("Foo")?.call0()?.downcast()?;
/// # let dict = &foo.borrow().inner;
/// # let dict: &PyDict = dict.as_ref(py);
/// #
/// # Ok(())
/// # })
/// # }
/// ```
///
/// This can also be done with other pyclasses:
/// ```rust
/// use pyo3::prelude::*;
///
/// #[pyclass]
/// struct Bar {/* ... */}
///
/// #[pyclass]
/// struct Foo {
/// inner: Py<Bar>,
/// }
///
/// #[pymethods]
/// impl Foo {
/// #[new]
/// fn __new__() -> PyResult<Foo> {
/// Python::with_gil(|py| {
/// let bar: Py<Bar> = Py::new(py, Bar {})?;
/// Ok(Foo { inner: bar })
/// })
/// }
/// }
/// #
/// # fn main() -> PyResult<()> {
/// # Python::with_gil(|py| {
/// # let m = pyo3::types::PyModule::new(py, "test")?;
/// # m.add_class::<Foo>()?;
/// #
/// # let foo: &PyCell<Foo> = m.getattr("Foo")?.call0()?.downcast()?;
/// # let bar = &foo.borrow().inner;
/// # let bar: &Bar = &*bar.borrow(py);
/// #
/// # Ok(())
/// # })
/// # }
/// ```
///
/// # Example: Shared ownership of Python objects
///
/// `Py<T>` can be used to share ownership of a Python object, similar to std's [`Rc`]`<T>`.
/// As with [`Rc`]`<T>`, cloning it increases its reference count rather than duplicating
/// the underlying object.
///
/// This can be done using either [`Py::clone_ref`] or [`Py`]`<T>`'s [`Clone`] trait implementation.
/// [`Py::clone_ref`] will be faster if you happen to be already holding the GIL.
///
/// ```rust
/// use pyo3::prelude::*;
/// use pyo3::types::PyDict;
///
/// # fn main() {
/// Python::with_gil(|py| {
/// let first: Py<PyDict> = PyDict::new_bound(py).unbind();
///
/// // All of these are valid syntax
/// let second = Py::clone_ref(&first, py);
/// let third = first.clone_ref(py);
/// let fourth = Py::clone(&first);
/// let fifth = first.clone();
///
/// // Disposing of our original `Py<PyDict>` just decrements the reference count.
/// drop(first);
///
/// // They all point to the same object
/// assert!(second.is(&third));
/// assert!(fourth.is(&fifth));
/// assert!(second.is(&fourth));
/// });
/// # }
/// ```
///
/// # Preventing reference cycles
///
/// It is easy to accidentally create reference cycles using [`Py`]`<T>`.
/// The Python interpreter can break these reference cycles within pyclasses if they
/// [integrate with the garbage collector][gc]. If your pyclass contains other Python
/// objects you should implement it to avoid leaking memory.
///
/// # A note on Python reference counts
///
/// Dropping a [`Py`]`<T>` will eventually decrease Python's reference count
/// of the pointed-to variable, allowing Python's garbage collector to free
/// the associated memory, but this may not happen immediately. This is
/// because a [`Py`]`<T>` can be dropped at any time, but the Python reference
/// count can only be modified when the GIL is held.
///
/// If a [`Py`]`<T>` is dropped while its thread happens to be holding the
/// GIL then the Python reference count will be decreased immediately.
/// Otherwise, the reference count will be decreased the next time the GIL is
/// reacquired.
///
/// If you happen to be already holding the GIL, [`Py::drop_ref`] will decrease
/// the Python reference count immediately and will execute slightly faster than
/// relying on implicit [`Drop`]s.
///
/// # A note on `Send` and `Sync`
///
/// Accessing this object is threadsafe, since any access to its API requires a [`Python<'py>`](crate::Python) token.
/// As you can only get this by acquiring the GIL, `Py<...>` implements [`Send`] and [`Sync`].
///
/// [`Rc`]: std::rc::Rc
/// [`RefCell`]: std::cell::RefCell
/// [gc]: https://pyo3.rs/main/class/protocols.html#garbage-collector-integration
#[repr(transparent)]
pub struct Py<T>(NonNull<ffi::PyObject>, PhantomData<T>);
// The inner value is only accessed through ways that require proving the gil is held
#[cfg(feature = "nightly")]
unsafe impl<T> crate::marker::Ungil for Py<T> {}
unsafe impl<T> Send for Py<T> {}
unsafe impl<T> Sync for Py<T> {}
impl<T> Py<T>
where
T: PyClass,
{
/// Creates a new instance `Py<T>` of a `#[pyclass]` on the Python heap.
///
/// # Examples
///
/// ```rust
/// use pyo3::prelude::*;
///
/// #[pyclass]
/// struct Foo {/* fields omitted */}
///
/// # fn main() -> PyResult<()> {
/// Python::with_gil(|py| -> PyResult<Py<Foo>> {
/// let foo: Py<Foo> = Py::new(py, Foo {})?;
/// Ok(foo)
/// })?;
/// # Ok(())
/// # }
/// ```
pub fn new(py: Python<'_>, value: impl Into<PyClassInitializer<T>>) -> PyResult<Py<T>> {
let initializer = value.into();
let obj = initializer.create_cell(py)?;
let ob = unsafe { Py::from_owned_ptr(py, obj as _) };
Ok(ob)
}
}
impl<T> Py<T>
where
T: HasPyGilRef,
{
/// Borrows a GIL-bound reference to the contained `T`.
///
/// By binding to the GIL lifetime, this allows the GIL-bound reference to not require
/// [`Python<'py>`](crate::Python) for any of its methods, which makes calling methods
/// on it more ergonomic.
///
/// For native types, this reference is `&T`. For pyclasses, this is `&PyCell<T>`.
///
/// Note that the lifetime of the returned reference is the shortest of `&self` and
/// [`Python<'py>`](crate::Python).
/// Consider using [`Py::into_ref`] instead if this poses a problem.
///
/// # Examples
///
/// Get access to `&PyList` from `Py<PyList>`:
///
/// ```
/// # use pyo3::prelude::*;
/// # use pyo3::types::PyList;
/// #
/// Python::with_gil(|py| {
/// let list: Py<PyList> = PyList::empty_bound(py).into();
/// let list: &PyList = list.as_ref(py);
/// assert_eq!(list.len(), 0);
/// });
/// ```
///
/// Get access to `&PyCell<MyClass>` from `Py<MyClass>`:
///
/// ```
/// # use pyo3::prelude::*;
/// #
/// #[pyclass]
/// struct MyClass {}
///
/// Python::with_gil(|py| {
/// let my_class: Py<MyClass> = Py::new(py, MyClass {}).unwrap();
/// let my_class_cell: &PyCell<MyClass> = my_class.as_ref(py);
/// assert!(my_class_cell.try_borrow().is_ok());
/// });
/// ```
pub fn as_ref<'py>(&'py self, _py: Python<'py>) -> &'py T::AsRefTarget {
let any = self.as_ptr() as *const PyAny;
unsafe { PyNativeType::unchecked_downcast(&*any) }
}
/// Borrows a GIL-bound reference to the contained `T` independently of the lifetime of `T`.
///
/// This method is similar to [`as_ref`](#method.as_ref) but consumes `self` and registers the
/// Python object reference in PyO3's object storage. The reference count for the Python
/// object will not be decreased until the GIL lifetime ends.
///
/// You should prefer using [`as_ref`](#method.as_ref) if you can as it'll have less overhead.
///
/// # Examples
///
/// [`Py::as_ref`]'s lifetime limitation forbids creating a function that references a
/// variable created inside the function.
///
/// ```rust,compile_fail
/// # use pyo3::prelude::*;
/// #
/// fn new_py_any<'py>(py: Python<'py>, value: impl IntoPy<Py<PyAny>>) -> &'py PyAny {
/// let obj: Py<PyAny> = value.into_py(py);
///
/// // The lifetime of the return value of this function is the shortest
/// // of `obj` and `py`. As `obj` is owned by the current function,
/// // Rust won't let the return value escape this function!
/// obj.as_ref(py)
/// }
/// ```
///
/// This can be solved by using [`Py::into_ref`] instead, which does not suffer from this issue.
/// Note that the lifetime of the [`Python<'py>`](crate::Python) token is transferred to
/// the returned reference.
///
/// ```rust
/// # use pyo3::prelude::*;
/// # #[allow(dead_code)] // This is just to show it compiles.
/// fn new_py_any<'py>(py: Python<'py>, value: impl IntoPy<Py<PyAny>>) -> &'py PyAny {
/// let obj: Py<PyAny> = value.into_py(py);
///
/// // This reference's lifetime is determined by `py`'s lifetime.
/// // Because that originates from outside this function,
/// // this return value is allowed.
/// obj.into_ref(py)
/// }
/// ```
pub fn into_ref(self, py: Python<'_>) -> &T::AsRefTarget {
unsafe { py.from_owned_ptr(self.into_ptr()) }
}
}
impl<T> Py<T> {
/// Returns the raw FFI pointer represented by self.
///
/// # Safety
///
/// Callers are responsible for ensuring that the pointer does not outlive self.
///
/// The reference is borrowed; callers should not decrease the reference count
/// when they are finished with the pointer.
#[inline]
pub fn as_ptr(&self) -> *mut ffi::PyObject {
self.0.as_ptr()
}
/// Returns an owned raw FFI pointer represented by self.
///
/// # Safety
///
/// The reference is owned; when finished the caller should either transfer ownership
/// of the pointer or decrease the reference count (e.g. with [`pyo3::ffi::Py_DecRef`](crate::ffi::Py_DecRef)).
#[inline]
pub fn into_ptr(self) -> *mut ffi::PyObject {
ManuallyDrop::new(self).0.as_ptr()
}
/// Helper to cast to `Py<PyAny>`.
#[inline]
pub fn as_any(&self) -> &Py<PyAny> {
// Safety: all Py<T> have the same memory layout, and all Py<T> are valid
// Py<PyAny>, so pointer casting is valid.
unsafe { &*(self as *const Self).cast::<Py<PyAny>>() }
}