1//! PyO3's interior mutability primitive.
2//!
3//! Rust has strict aliasing rules - you can either have any number of immutable (shared) references or one mutable
4//! reference. Python's ownership model is the complete opposite of that - any Python object
5//! can be referenced any number of times, and mutation is allowed from any reference.
6//!
7//! PyO3 deals with these differences by employing the [Interior Mutability]
8//! pattern. This requires that PyO3 enforces the borrowing rules and it has two mechanisms for
9//! doing so:
10//! - Statically it can enforce thread-safe access with the [`Python<'py>`](crate::Python) token.
11//! All Rust code holding that token, or anything derived from it, can assume that they have
12//! safe access to the Python interpreter's state. For this reason all the native Python objects
13//! can be mutated through shared references.
14//! - However, methods and functions in Rust usually *do* need `&mut` references. While PyO3 can
15//! use the [`Python<'py>`](crate::Python) token to guarantee thread-safe access to them, it cannot
16//! statically guarantee uniqueness of `&mut` references. As such those references have to be tracked
17//! dynamically at runtime, using `PyCell` and the other types defined in this module. This works
18//! similar to std's [`RefCell`](std::cell::RefCell) type.
19//!
20//! # When *not* to use PyCell
21//!
22//! Usually you can use `&mut` references as method and function receivers and arguments, and you
23//! won't need to use `PyCell` directly:
24//!
25//! ```rust
26//! use pyo3::prelude::*;
27//!
28//! #[pyclass]
29//! struct Number {
30//! inner: u32,
31//! }
32//!
33//! #[pymethods]
34//! impl Number {
35//! fn increment(&mut self) {
36//! self.inner += 1;
37//! }
38//! }
39//! ```
40//!
41//! The [`#[pymethods]`](crate::pymethods) proc macro will generate this wrapper function (and more),
42//! using `PyCell` under the hood:
43//!
44//! ```rust,ignore
45//! # use pyo3::prelude::*;
46//! # #[pyclass]
47//! # struct Number {
48//! # inner: u32,
49//! # }
50//! #
51//! # #[pymethods]
52//! # impl Number {
53//! # fn increment(&mut self) {
54//! # self.inner += 1;
55//! # }
56//! # }
57//! #
58//! // The function which is exported to Python looks roughly like the following
59//! unsafe extern "C" fn __pymethod_increment__(
60//! _slf: *mut pyo3::ffi::PyObject,
61//! _args: *mut pyo3::ffi::PyObject,
62//! ) -> *mut pyo3::ffi::PyObject {
63//! use :: pyo3 as _pyo3;
64//! _pyo3::impl_::trampoline::noargs(_slf, _args, |py, _slf| {
65//! # #[allow(deprecated)]
66//! let _cell = py
67//! .from_borrowed_ptr::<_pyo3::PyAny>(_slf)
68//! .downcast::<_pyo3::PyCell<Number>>()?;
69//! let mut _ref = _cell.try_borrow_mut()?;
70//! let _slf: &mut Number = &mut *_ref;
71//! _pyo3::impl_::callback::convert(py, Number::increment(_slf))
72//! })
73//! }
74//! ```
75//!
76//! # When to use PyCell
77//! ## Using pyclasses from Rust
78//!
79//! However, we *do* need `PyCell` if we want to call its methods from Rust:
80//! ```rust
81//! # use pyo3::prelude::*;
82//! #
83//! # #[pyclass]
84//! # struct Number {
85//! # inner: u32,
86//! # }
87//! #
88//! # #[pymethods]
89//! # impl Number {
90//! # fn increment(&mut self) {
91//! # self.inner += 1;
92//! # }
93//! # }
94//! # fn main() -> PyResult<()> {
95//! Python::with_gil(|py| {
96//! let n = Py::new(py, Number { inner: 0 })?;
97//!
98//! // We borrow the guard and then dereference
99//! // it to get a mutable reference to Number
100//! let mut guard: PyRefMut<'_, Number> = n.bind(py).borrow_mut();
101//! let n_mutable: &mut Number = &mut *guard;
102//!
103//! n_mutable.increment();
104//!
105//! // To avoid panics we must dispose of the
106//! // `PyRefMut` before borrowing again.
107//! drop(guard);
108//!
109//! let n_immutable: &Number = &n.bind(py).borrow();
110//! assert_eq!(n_immutable.inner, 1);
111//!
112//! Ok(())
113//! })
114//! # }
115//! ```
116//! ## Dealing with possibly overlapping mutable references
117//!
118//! It is also necessary to use `PyCell` if you can receive mutable arguments that may overlap.
119//! Suppose the following function that swaps the values of two `Number`s:
120//! ```
121//! # use pyo3::prelude::*;
122//! # #[pyclass]
123//! # pub struct Number {
124//! # inner: u32,
125//! # }
126//! #[pyfunction]
127//! fn swap_numbers(a: &mut Number, b: &mut Number) {
128//! std::mem::swap(&mut a.inner, &mut b.inner);
129//! }
130//! # fn main() {
131//! # Python::with_gil(|py| {
132//! # let n = Py::new(py, Number{inner: 35}).unwrap();
133//! # let n2 = n.clone_ref(py);
134//! # assert!(n.is(&n2));
135//! # let fun = pyo3::wrap_pyfunction!(swap_numbers, py).unwrap();
136//! # fun.call1((n, n2)).expect_err("Managed to create overlapping mutable references. Note: this is undefined behaviour.");
137//! # });
138//! # }
139//! ```
140//! When users pass in the same `Number` as both arguments, one of the mutable borrows will
141//! fail and raise a `RuntimeError`:
142//! ```text
143//! >>> a = Number()
144//! >>> swap_numbers(a, a)
145//! Traceback (most recent call last):
146//! File "<stdin>", line 1, in <module>
147//! RuntimeError: Already borrowed
148//! ```
149//!
150//! It is better to write that function like this:
151//! ```rust,ignore
152//! # #![allow(deprecated)]
153//! # use pyo3::prelude::*;
154//! # #[pyclass]
155//! # pub struct Number {
156//! # inner: u32,
157//! # }
158//! #[pyfunction]
159//! fn swap_numbers(a: &PyCell<Number>, b: &PyCell<Number>) {
160//! // Check that the pointers are unequal
161//! if !a.is(b) {
162//! std::mem::swap(&mut a.borrow_mut().inner, &mut b.borrow_mut().inner);
163//! } else {
164//! // Do nothing - they are the same object, so don't need swapping.
165//! }
166//! }
167//! # fn main() {
168//! # // With duplicate numbers
169//! # Python::with_gil(|py| {
170//! # let n = Py::new(py, Number{inner: 35}).unwrap();
171//! # let n2 = n.clone_ref(py);
172//! # assert!(n.is(&n2));
173//! # let fun = pyo3::wrap_pyfunction!(swap_numbers, py).unwrap();
174//! # fun.call1((n, n2)).unwrap();
175//! # });
176//! #
177//! # // With two different numbers
178//! # Python::with_gil(|py| {
179//! # let n = Py::new(py, Number{inner: 35}).unwrap();
180//! # let n2 = Py::new(py, Number{inner: 42}).unwrap();
181//! # assert!(!n.is(&n2));
182//! # let fun = pyo3::wrap_pyfunction!(swap_numbers, py).unwrap();
183//! # fun.call1((&n, &n2)).unwrap();
184//! # let n: u32 = n.borrow(py).inner;
185//! # let n2: u32 = n2.borrow(py).inner;
186//! # assert_eq!(n, 42);
187//! # assert_eq!(n2, 35);
188//! # });
189//! # }
190//! ```
191//! See the [guide] for more information.
192//!
193//! [guide]: https://pyo3.rs/latest/class.html#pycell-and-interior-mutability "PyCell and interior mutability"
194//! [Interior Mutability]: https://doc.rust-lang.org/book/ch15-05-interior-mutability.html "RefCell<T> and the Interior Mutability Pattern - The Rust Programming Language"
195
196use crate::conversion::{AsPyPointer, IntoPyObject};
197use crate::exceptions::PyRuntimeError;
198use crate::ffi_ptr_ext::FfiPtrExt;
199use crate::internal_tricks::{ptr_from_mut, ptr_from_ref};
200use crate::pyclass::{boolean_struct::False, PyClass};
201use crate::types::any::PyAnyMethods;
202#[allow(deprecated)]
203use crate::IntoPy;
204use crate::{ffi, Borrowed, Bound, PyErr, PyObject, Python};
205use std::convert::Infallible;
206use std::fmt;
207use std::mem::ManuallyDrop;
208use std::ops::{Deref, DerefMut};
209
210pub(crate) mod impl_;
211use impl_::{PyClassBorrowChecker, PyClassObjectLayout};
212
213/// A wrapper type for an immutably borrowed value from a [`Bound<'py, T>`].
214///
215/// See the [`Bound`] documentation for more information.
216///
217/// # Examples
218///
219/// You can use [`PyRef`] as an alternative to a `&self` receiver when
220/// - you need to access the pointer of the [`Bound`], or
221/// - you want to get a super class.
222/// ```
223/// # use pyo3::prelude::*;
224/// #[pyclass(subclass)]
225/// struct Parent {
226/// basename: &'static str,
227/// }
228///
229/// #[pyclass(extends=Parent)]
230/// struct Child {
231/// name: &'static str,
232/// }
233///
234/// #[pymethods]
235/// impl Child {
236/// #[new]
237/// fn new() -> (Self, Parent) {
238/// (Child { name: "Caterpillar" }, Parent { basename: "Butterfly" })
239/// }
240///
241/// fn format(slf: PyRef<'_, Self>) -> String {
242/// // We can get *mut ffi::PyObject from PyRef
243/// let refcnt = unsafe { pyo3::ffi::Py_REFCNT(slf.as_ptr()) };
244/// // We can get &Self::BaseType by as_ref
245/// let basename = slf.as_ref().basename;
246/// format!("{}(base: {}, cnt: {})", slf.name, basename, refcnt)
247/// }
248/// }
249/// # Python::with_gil(|py| {
250/// # let sub = Py::new(py, Child::new()).unwrap();
251/// # pyo3::py_run!(py, sub, "assert sub.format() == 'Caterpillar(base: Butterfly, cnt: 4)', sub.format()");
252/// # });
253/// ```
254///
255/// See the [module-level documentation](self) for more information.
256#[repr(transparent)]
257pub struct PyRef<'p, T: PyClass> {
258 // TODO: once the GIL Ref API is removed, consider adding a lifetime parameter to `PyRef` to
259 // store `Borrowed` here instead, avoiding reference counting overhead.
260 inner: Bound<'p, T>,
261}
262
263impl<'p, T: PyClass> PyRef<'p, T> {
264 /// Returns a `Python` token that is bound to the lifetime of the `PyRef`.
265 pub fn py(&self) -> Python<'p> {
266 self.inner.py()
267 }
268}
269
270impl<T, U> AsRef<U> for PyRef<'_, T>
271where
272 T: PyClass<BaseType = U>,
273 U: PyClass,
274{
275 fn as_ref(&self) -> &T::BaseType {
276 self.as_super()
277 }
278}
279
280impl<'py, T: PyClass> PyRef<'py, T> {
281 /// Returns the raw FFI pointer represented by self.
282 ///
283 /// # Safety
284 ///
285 /// Callers are responsible for ensuring that the pointer does not outlive self.
286 ///
287 /// The reference is borrowed; callers should not decrease the reference count
288 /// when they are finished with the pointer.
289 #[inline]
290 pub fn as_ptr(&self) -> *mut ffi::PyObject {
291 self.inner.as_ptr()
292 }
293
294 /// Returns an owned raw FFI pointer represented by self.
295 ///
296 /// # Safety
297 ///
298 /// The reference is owned; when finished the caller should either transfer ownership
299 /// of the pointer or decrease the reference count (e.g. with [`pyo3::ffi::Py_DecRef`](crate::ffi::Py_DecRef)).
300 #[inline]
301 pub fn into_ptr(self) -> *mut ffi::PyObject {
302 self.inner.clone().into_ptr()
303 }
304
305 #[track_caller]
306 pub(crate) fn borrow(obj: &Bound<'py, T>) -> Self {
307 Self::try_borrow(obj).expect("Already mutably borrowed")
308 }
309
310 pub(crate) fn try_borrow(obj: &Bound<'py, T>) -> Result<Self, PyBorrowError> {
311 let cell = obj.get_class_object();
312 cell.ensure_threadsafe();
313 cell.borrow_checker()
314 .try_borrow()
315 .map(|_| Self { inner: obj.clone() })
316 }
317}
318
319impl<'p, T, U> PyRef<'p, T>
320where
321 T: PyClass<BaseType = U>,
322 U: PyClass,
323{
324 /// Gets a `PyRef<T::BaseType>`.
325 ///
326 /// While `as_ref()` returns a reference of type `&T::BaseType`, this cannot be
327 /// used to get the base of `T::BaseType`.
328 ///
329 /// But with the help of this method, you can get hold of instances of the
330 /// super-superclass when needed.
331 ///
332 /// # Examples
333 /// ```
334 /// # use pyo3::prelude::*;
335 /// #[pyclass(subclass)]
336 /// struct Base1 {
337 /// name1: &'static str,
338 /// }
339 ///
340 /// #[pyclass(extends=Base1, subclass)]
341 /// struct Base2 {
342 /// name2: &'static str,
343 /// }
344 ///
345 /// #[pyclass(extends=Base2)]
346 /// struct Sub {
347 /// name3: &'static str,
348 /// }
349 ///
350 /// #[pymethods]
351 /// impl Sub {
352 /// #[new]
353 /// fn new() -> PyClassInitializer<Self> {
354 /// PyClassInitializer::from(Base1 { name1: "base1" })
355 /// .add_subclass(Base2 { name2: "base2" })
356 /// .add_subclass(Self { name3: "sub" })
357 /// }
358 /// fn name(slf: PyRef<'_, Self>) -> String {
359 /// let subname = slf.name3;
360 /// let super_ = slf.into_super();
361 /// format!("{} {} {}", super_.as_ref().name1, super_.name2, subname)
362 /// }
363 /// }
364 /// # Python::with_gil(|py| {
365 /// # let sub = Py::new(py, Sub::new()).unwrap();
366 /// # pyo3::py_run!(py, sub, "assert sub.name() == 'base1 base2 sub'")
367 /// # });
368 /// ```
369 pub fn into_super(self) -> PyRef<'p, U> {
370 let py = self.py();
371 PyRef {
372 inner: unsafe {
373 ManuallyDrop::new(self)
374 .as_ptr()
375 .assume_owned_unchecked(py)
376 .downcast_into_unchecked()
377 },
378 }
379 }
380
381 /// Borrows a shared reference to `PyRef<T::BaseType>`.
382 ///
383 /// With the help of this method, you can access attributes and call methods
384 /// on the superclass without consuming the `PyRef<T>`. This method can also
385 /// be chained to access the super-superclass (and so on).
386 ///
387 /// # Examples
388 /// ```
389 /// # use pyo3::prelude::*;
390 /// #[pyclass(subclass)]
391 /// struct Base {
392 /// base_name: &'static str,
393 /// }
394 /// #[pymethods]
395 /// impl Base {
396 /// fn base_name_len(&self) -> usize {
397 /// self.base_name.len()
398 /// }
399 /// }
400 ///
401 /// #[pyclass(extends=Base)]
402 /// struct Sub {
403 /// sub_name: &'static str,
404 /// }
405 ///
406 /// #[pymethods]
407 /// impl Sub {
408 /// #[new]
409 /// fn new() -> (Self, Base) {
410 /// (Self { sub_name: "sub_name" }, Base { base_name: "base_name" })
411 /// }
412 /// fn sub_name_len(&self) -> usize {
413 /// self.sub_name.len()
414 /// }
415 /// fn format_name_lengths(slf: PyRef<'_, Self>) -> String {
416 /// format!("{} {}", slf.as_super().base_name_len(), slf.sub_name_len())
417 /// }
418 /// }
419 /// # Python::with_gil(|py| {
420 /// # let sub = Py::new(py, Sub::new()).unwrap();
421 /// # pyo3::py_run!(py, sub, "assert sub.format_name_lengths() == '9 8'")
422 /// # });
423 /// ```
424 pub fn as_super(&self) -> &PyRef<'p, U> {
425 let ptr = ptr_from_ref::<Bound<'p, T>>(&self.inner)
426 // `Bound<T>` has the same layout as `Bound<T::BaseType>`
427 .cast::<Bound<'p, T::BaseType>>()
428 // `Bound<T::BaseType>` has the same layout as `PyRef<T::BaseType>`
429 .cast::<PyRef<'p, T::BaseType>>();
430 unsafe { &*ptr }
431 }
432}
433
434impl<T: PyClass> Deref for PyRef<'_, T> {
435 type Target = T;
436
437 #[inline]
438 fn deref(&self) -> &T {
439 unsafe { &*self.inner.get_class_object().get_ptr() }
440 }
441}
442
443impl<T: PyClass> Drop for PyRef<'_, T> {
444 fn drop(&mut self) {
445 self.inner
446 .get_class_object()
447 .borrow_checker()
448 .release_borrow()
449 }
450}
451
452#[allow(deprecated)]
453impl<T: PyClass> IntoPy<PyObject> for PyRef<'_, T> {
454 fn into_py(self, py: Python<'_>) -> PyObject {
455 unsafe { PyObject::from_borrowed_ptr(py, self.inner.as_ptr()) }
456 }
457}
458
459#[allow(deprecated)]
460impl<T: PyClass> IntoPy<PyObject> for &'_ PyRef<'_, T> {
461 fn into_py(self, py: Python<'_>) -> PyObject {
462 unsafe { PyObject::from_borrowed_ptr(py, self.inner.as_ptr()) }
463 }
464}
465
466impl<'py, T: PyClass> IntoPyObject<'py> for PyRef<'py, T> {
467 type Target = T;
468 type Output = Bound<'py, T>;
469 type Error = Infallible;
470
471 fn into_pyobject(self, _py: Python<'py>) -> Result<Self::Output, Self::Error> {
472 Ok(self.inner.clone())
473 }
474}
475
476impl<'a, 'py, T: PyClass> IntoPyObject<'py> for &'a PyRef<'py, T> {
477 type Target = T;
478 type Output = Borrowed<'a, 'py, T>;
479 type Error = Infallible;
480
481 fn into_pyobject(self, _py: Python<'py>) -> Result<Self::Output, Self::Error> {
482 Ok(self.inner.as_borrowed())
483 }
484}
485
486unsafe impl<T: PyClass> AsPyPointer for PyRef<'_, T> {
487 fn as_ptr(&self) -> *mut ffi::PyObject {
488 self.inner.as_ptr()
489 }
490}
491
492impl<T: PyClass + fmt::Debug> fmt::Debug for PyRef<'_, T> {
493 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
494 fmt::Debug::fmt(&**self, f)
495 }
496}
497
498/// A wrapper type for a mutably borrowed value from a [`Bound<'py, T>`].
499///
500/// See the [module-level documentation](self) for more information.
501#[repr(transparent)]
502pub struct PyRefMut<'p, T: PyClass<Frozen = False>> {
503 // TODO: once the GIL Ref API is removed, consider adding a lifetime parameter to `PyRef` to
504 // store `Borrowed` here instead, avoiding reference counting overhead.
505 inner: Bound<'p, T>,
506}
507
508impl<'p, T: PyClass<Frozen = False>> PyRefMut<'p, T> {
509 /// Returns a `Python` token that is bound to the lifetime of the `PyRefMut`.
510 pub fn py(&self) -> Python<'p> {
511 self.inner.py()
512 }
513}
514
515impl<T, U> AsRef<U> for PyRefMut<'_, T>
516where
517 T: PyClass<BaseType = U, Frozen = False>,
518 U: PyClass<Frozen = False>,
519{
520 fn as_ref(&self) -> &T::BaseType {
521 PyRefMut::downgrade(self).as_super()
522 }
523}
524
525impl<T, U> AsMut<U> for PyRefMut<'_, T>
526where
527 T: PyClass<BaseType = U, Frozen = False>,
528 U: PyClass<Frozen = False>,
529{
530 fn as_mut(&mut self) -> &mut T::BaseType {
531 self.as_super()
532 }
533}
534
535impl<'py, T: PyClass<Frozen = False>> PyRefMut<'py, T> {
536 /// Returns the raw FFI pointer represented by self.
537 ///
538 /// # Safety
539 ///
540 /// Callers are responsible for ensuring that the pointer does not outlive self.
541 ///
542 /// The reference is borrowed; callers should not decrease the reference count
543 /// when they are finished with the pointer.
544 #[inline]
545 pub fn as_ptr(&self) -> *mut ffi::PyObject {
546 self.inner.as_ptr()
547 }
548
549 /// Returns an owned raw FFI pointer represented by self.
550 ///
551 /// # Safety
552 ///
553 /// The reference is owned; when finished the caller should either transfer ownership
554 /// of the pointer or decrease the reference count (e.g. with [`pyo3::ffi::Py_DecRef`](crate::ffi::Py_DecRef)).
555 #[inline]
556 pub fn into_ptr(self) -> *mut ffi::PyObject {
557 self.inner.clone().into_ptr()
558 }
559
560 #[inline]
561 #[track_caller]
562 pub(crate) fn borrow(obj: &Bound<'py, T>) -> Self {
563 Self::try_borrow(obj).expect("Already borrowed")
564 }
565
566 pub(crate) fn try_borrow(obj: &Bound<'py, T>) -> Result<Self, PyBorrowMutError> {
567 let cell = obj.get_class_object();
568 cell.ensure_threadsafe();
569 cell.borrow_checker()
570 .try_borrow_mut()
571 .map(|_| Self { inner: obj.clone() })
572 }
573
574 pub(crate) fn downgrade(slf: &Self) -> &PyRef<'py, T> {
575 // `PyRefMut<T>` and `PyRef<T>` have the same layout
576 unsafe { &*ptr_from_ref(slf).cast() }
577 }
578}
579
580impl<'p, T, U> PyRefMut<'p, T>
581where
582 T: PyClass<BaseType = U, Frozen = False>,
583 U: PyClass<Frozen = False>,
584{
585 /// Gets a `PyRef<T::BaseType>`.
586 ///
587 /// See [`PyRef::into_super`] for more.
588 pub fn into_super(self) -> PyRefMut<'p, U> {
589 let py = self.py();
590 PyRefMut {
591 inner: unsafe {
592 ManuallyDrop::new(self)
593 .as_ptr()
594 .assume_owned_unchecked(py)
595 .downcast_into_unchecked()
596 },
597 }
598 }
599
600 /// Borrows a mutable reference to `PyRefMut<T::BaseType>`.
601 ///
602 /// With the help of this method, you can mutate attributes and call mutating
603 /// methods on the superclass without consuming the `PyRefMut<T>`. This method
604 /// can also be chained to access the super-superclass (and so on).
605 ///
606 /// See [`PyRef::as_super`] for more.
607 pub fn as_super(&mut self) -> &mut PyRefMut<'p, U> {
608 let ptr = ptr_from_mut::<Bound<'p, T>>(&mut self.inner)
609 // `Bound<T>` has the same layout as `Bound<T::BaseType>`
610 .cast::<Bound<'p, T::BaseType>>()
611 // `Bound<T::BaseType>` has the same layout as `PyRefMut<T::BaseType>`,
612 // and the mutable borrow on `self` prevents aliasing
613 .cast::<PyRefMut<'p, T::BaseType>>();
614 unsafe { &mut *ptr }
615 }
616}
617
618impl<T: PyClass<Frozen = False>> Deref for PyRefMut<'_, T> {
619 type Target = T;
620
621 #[inline]
622 fn deref(&self) -> &T {
623 unsafe { &*self.inner.get_class_object().get_ptr() }
624 }
625}
626
627impl<T: PyClass<Frozen = False>> DerefMut for PyRefMut<'_, T> {
628 #[inline]
629 fn deref_mut(&mut self) -> &mut T {
630 unsafe { &mut *self.inner.get_class_object().get_ptr() }
631 }
632}
633
634impl<T: PyClass<Frozen = False>> Drop for PyRefMut<'_, T> {
635 fn drop(&mut self) {
636 self.inner
637 .get_class_object()
638 .borrow_checker()
639 .release_borrow_mut()
640 }
641}
642
643#[allow(deprecated)]
644impl<T: PyClass<Frozen = False>> IntoPy<PyObject> for PyRefMut<'_, T> {
645 fn into_py(self, py: Python<'_>) -> PyObject {
646 unsafe { PyObject::from_borrowed_ptr(py, self.inner.as_ptr()) }
647 }
648}
649
650#[allow(deprecated)]
651impl<T: PyClass<Frozen = False>> IntoPy<PyObject> for &'_ PyRefMut<'_, T> {
652 fn into_py(self, py: Python<'_>) -> PyObject {
653 self.inner.clone().into_py(py)
654 }
655}
656
657impl<'py, T: PyClass<Frozen = False>> IntoPyObject<'py> for PyRefMut<'py, T> {
658 type Target = T;
659 type Output = Bound<'py, T>;
660 type Error = Infallible;
661
662 fn into_pyobject(self, _py: Python<'py>) -> Result<Self::Output, Self::Error> {
663 Ok(self.inner.clone())
664 }
665}
666
667impl<'a, 'py, T: PyClass<Frozen = False>> IntoPyObject<'py> for &'a PyRefMut<'py, T> {
668 type Target = T;
669 type Output = Borrowed<'a, 'py, T>;
670 type Error = Infallible;
671
672 fn into_pyobject(self, _py: Python<'py>) -> Result<Self::Output, Self::Error> {
673 Ok(self.inner.as_borrowed())
674 }
675}
676
677impl<T: PyClass<Frozen = False> + fmt::Debug> fmt::Debug for PyRefMut<'_, T> {
678 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
679 fmt::Debug::fmt(self.deref(), f)
680 }
681}
682
683/// An error type returned by [`Bound::try_borrow`].
684///
685/// If this error is allowed to bubble up into Python code it will raise a `RuntimeError`.
686pub struct PyBorrowError {
687 _private: (),
688}
689
690impl fmt::Debug for PyBorrowError {
691 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
692 f.debug_struct(name:"PyBorrowError").finish()
693 }
694}
695
696impl fmt::Display for PyBorrowError {
697 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
698 fmt::Display::fmt(self:"Already mutably borrowed", f)
699 }
700}
701
702impl From<PyBorrowError> for PyErr {
703 fn from(other: PyBorrowError) -> Self {
704 PyRuntimeError::new_err(args:other.to_string())
705 }
706}
707
708/// An error type returned by [`Bound::try_borrow_mut`].
709///
710/// If this error is allowed to bubble up into Python code it will raise a `RuntimeError`.
711pub struct PyBorrowMutError {
712 _private: (),
713}
714
715impl fmt::Debug for PyBorrowMutError {
716 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
717 f.debug_struct(name:"PyBorrowMutError").finish()
718 }
719}
720
721impl fmt::Display for PyBorrowMutError {
722 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
723 fmt::Display::fmt(self:"Already borrowed", f)
724 }
725}
726
727impl From<PyBorrowMutError> for PyErr {
728 fn from(other: PyBorrowMutError) -> Self {
729 PyRuntimeError::new_err(args:other.to_string())
730 }
731}
732
733#[cfg(test)]
734#[cfg(feature = "macros")]
735mod tests {
736
737 use super::*;
738
739 #[crate::pyclass]
740 #[pyo3(crate = "crate")]
741 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
742 struct SomeClass(i32);
743
744 #[test]
745 fn test_as_ptr() {
746 Python::with_gil(|py| {
747 let cell = Bound::new(py, SomeClass(0)).unwrap();
748 let ptr = cell.as_ptr();
749
750 assert_eq!(cell.borrow().as_ptr(), ptr);
751 assert_eq!(cell.borrow_mut().as_ptr(), ptr);
752 })
753 }
754
755 #[test]
756 fn test_into_ptr() {
757 Python::with_gil(|py| {
758 let cell = Bound::new(py, SomeClass(0)).unwrap();
759 let ptr = cell.as_ptr();
760
761 assert_eq!(cell.borrow().into_ptr(), ptr);
762 unsafe { ffi::Py_DECREF(ptr) };
763
764 assert_eq!(cell.borrow_mut().into_ptr(), ptr);
765 unsafe { ffi::Py_DECREF(ptr) };
766 })
767 }
768
769 #[crate::pyclass]
770 #[pyo3(crate = "crate", subclass)]
771 struct BaseClass {
772 val1: usize,
773 }
774
775 #[crate::pyclass]
776 #[pyo3(crate = "crate", extends=BaseClass, subclass)]
777 struct SubClass {
778 val2: usize,
779 }
780
781 #[crate::pyclass]
782 #[pyo3(crate = "crate", extends=SubClass)]
783 struct SubSubClass {
784 val3: usize,
785 }
786
787 #[crate::pymethods]
788 #[pyo3(crate = "crate")]
789 impl SubSubClass {
790 #[new]
791 fn new(py: Python<'_>) -> crate::Py<SubSubClass> {
792 let init = crate::PyClassInitializer::from(BaseClass { val1: 10 })
793 .add_subclass(SubClass { val2: 15 })
794 .add_subclass(SubSubClass { val3: 20 });
795 crate::Py::new(py, init).expect("allocation error")
796 }
797
798 fn get_values(self_: PyRef<'_, Self>) -> (usize, usize, usize) {
799 let val1 = self_.as_super().as_super().val1;
800 let val2 = self_.as_super().val2;
801 (val1, val2, self_.val3)
802 }
803
804 fn double_values(mut self_: PyRefMut<'_, Self>) {
805 self_.as_super().as_super().val1 *= 2;
806 self_.as_super().val2 *= 2;
807 self_.val3 *= 2;
808 }
809 }
810
811 #[test]
812 fn test_pyref_as_super() {
813 Python::with_gil(|py| {
814 let obj = SubSubClass::new(py).into_bound(py);
815 let pyref = obj.borrow();
816 assert_eq!(pyref.as_super().as_super().val1, 10);
817 assert_eq!(pyref.as_super().val2, 15);
818 assert_eq!(pyref.as_ref().val2, 15); // `as_ref` also works
819 assert_eq!(pyref.val3, 20);
820 assert_eq!(SubSubClass::get_values(pyref), (10, 15, 20));
821 });
822 }
823
824 #[test]
825 fn test_pyrefmut_as_super() {
826 Python::with_gil(|py| {
827 let obj = SubSubClass::new(py).into_bound(py);
828 assert_eq!(SubSubClass::get_values(obj.borrow()), (10, 15, 20));
829 {
830 let mut pyrefmut = obj.borrow_mut();
831 assert_eq!(pyrefmut.as_super().as_ref().val1, 10);
832 pyrefmut.as_super().as_super().val1 -= 5;
833 pyrefmut.as_super().val2 -= 3;
834 pyrefmut.as_mut().val2 -= 2; // `as_mut` also works
835 pyrefmut.val3 -= 5;
836 }
837 assert_eq!(SubSubClass::get_values(obj.borrow()), (5, 10, 15));
838 SubSubClass::double_values(obj.borrow_mut());
839 assert_eq!(SubSubClass::get_values(obj.borrow()), (10, 20, 30));
840 });
841 }
842
843 #[test]
844 fn test_pyrefs_in_python() {
845 Python::with_gil(|py| {
846 let obj = SubSubClass::new(py);
847 crate::py_run!(py, obj, "assert obj.get_values() == (10, 15, 20)");
848 crate::py_run!(py, obj, "assert obj.double_values() is None");
849 crate::py_run!(py, obj, "assert obj.get_values() == (20, 30, 40)");
850 });
851 }
852}
853