Struct pyo3::types::PyWeakrefReference

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pub struct PyWeakrefReference(/* private fields */);
Expand description

Represents a Python weakref.ReferenceType.

In Python this is created by calling weakref.ref.

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impl PyWeakrefReference

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pub fn new_bound<'py>( object: &Bound<'py, PyAny>, ) -> PyResult<Bound<'py, PyWeakrefReference>>

Constructs a new Weak Reference (weakref.ref/weakref.ReferenceType) for the given object.

Returns a TypeError if object is not weak referenceable (Most native types and PyClasses without weakref flag).

§Examples
use pyo3::prelude::*;
use pyo3::types::PyWeakrefReference;

#[pyclass(weakref)]
struct Foo { /* fields omitted */ }

Python::with_gil(|py| {
    let foo = Bound::new(py, Foo {})?;
    let weakref = PyWeakrefReference::new_bound(&foo)?;
    assert!(
        // In normal situations where a direct `Bound<'py, Foo>` is required use `upgrade::<Foo>`
        weakref.upgrade()
            .map_or(false, |obj| obj.is(&foo))
    );

    let weakref2 = PyWeakrefReference::new_bound(&foo)?;
    assert!(weakref.is(&weakref2));

    drop(foo);

    assert!(weakref.upgrade().is_none());
    Ok(())
})
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pub fn new_bound_with<'py, C>( object: &Bound<'py, PyAny>, callback: C, ) -> PyResult<Bound<'py, PyWeakrefReference>>
where C: ToPyObject,

Constructs a new Weak Reference (weakref.ref/weakref.ReferenceType) for the given object with a callback.

Returns a TypeError if object is not weak referenceable (Most native types and PyClasses without weakref flag) or if the callback is not callable or None.

§Examples
use pyo3::prelude::*;
use pyo3::types::PyWeakrefReference;

#[pyclass(weakref)]
struct Foo { /* fields omitted */ }

#[pyfunction]
fn callback(wref: Bound<'_, PyWeakrefReference>) -> PyResult<()> {
        let py = wref.py();
        assert!(wref.upgrade_as::<Foo>()?.is_none());
        py.run_bound("counter = 1", None, None)
}

Python::with_gil(|py| {
    py.run_bound("counter = 0", None, None)?;
    assert_eq!(py.eval_bound("counter", None, None)?.extract::<u32>()?, 0);
    let foo = Bound::new(py, Foo{})?;

    // This is fine.
    let weakref = PyWeakrefReference::new_bound_with(&foo, py.None())?;
    assert!(weakref.upgrade_as::<Foo>()?.is_some());
    assert!(
        // In normal situations where a direct `Bound<'py, Foo>` is required use `upgrade::<Foo>`
        weakref.upgrade()
            .map_or(false, |obj| obj.is(&foo))
    );
    assert_eq!(py.eval_bound("counter", None, None)?.extract::<u32>()?, 0);

    let weakref2 = PyWeakrefReference::new_bound_with(&foo, wrap_pyfunction_bound!(callback, py)?)?;
    assert!(!weakref.is(&weakref2)); // Not the same weakref
    assert!(weakref.eq(&weakref2)?);  // But Equal, since they point to the same object

    drop(foo);

    assert!(weakref.upgrade_as::<Foo>()?.is_none());
    assert_eq!(py.eval_bound("counter", None, None)?.extract::<u32>()?, 1);
    Ok(())
})

Trait Implementations§

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impl AsPyPointer for PyWeakrefReference

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fn as_ptr(&self) -> *mut PyObject

Gets the underlying FFI pointer, returns a borrowed pointer.

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impl AsRef<PyAny> for PyWeakrefReference

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fn as_ref(&self) -> &PyAny

Converts this type into a shared reference of the (usually inferred) input type.
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impl Deref for PyWeakrefReference

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type Target = PyAny

The resulting type after dereferencing.
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fn deref(&self) -> &PyAny

Dereferences the value.
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impl PyTypeInfo for PyWeakrefReference

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const NAME: &'static str = "PyWeakrefReference"

Class name.
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const MODULE: Option<&'static str> = _

Module name, if any.
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fn type_object_raw(py: Python<'_>) -> *mut PyTypeObject

Returns the PyTypeObject instance for this type.
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fn is_type_of_bound(obj: &Bound<'_, PyAny>) -> bool

Checks if object is an instance of this type or a subclass of this type.
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fn type_object_bound(py: Python<'_>) -> Bound<'_, PyType>

Returns the safe abstraction over the type object.
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fn is_exact_type_of_bound(object: &Bound<'_, PyAny>) -> bool

Checks if object is an instance of this type.
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impl DerefToPyAny for PyWeakrefReference

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impl PyLayout<PyWeakrefReference> for PyWeakReference

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impl PySizedLayout<PyWeakrefReference> for PyWeakReference

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> IntoEither for T

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fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts self into a Left variant of Either<Self, Self> if into_left is true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts self into a Left variant of Either<Self, Self> if into_left(&self) returns true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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impl<T> PyTypeCheck for T
where T: PyTypeInfo,

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const NAME: &'static str = const NAME: &'static str = <T as PyTypeInfo>::NAME;

Name of self. This is used in error messages, for example.
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fn type_check(object: &Bound<'_, PyAny>) -> bool

Checks if object is an instance of Self, which may include a subtype. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.