Struct pyo3::types::PyCapsule

source · [−]
#[repr(transparent)]
pub struct PyCapsule(_);
Expand description

Represents a Python Capsule as described in Capsules:

This subtype of PyObject represents an opaque value, useful for C extension modules who need to pass an opaque value (as a void* pointer) through Python code to other C code. It is often used to make a C function pointer defined in one module available to other modules, so the regular import mechanism can be used to access C APIs defined in dynamically loaded modules.

Example

 use std::ffi::CString;
 use pyo3::{prelude::*, types::PyCapsule};

 #[repr(C)]
 struct Foo {
     pub val: u32,
 }

 let r = Python::with_gil(|py| -> PyResult<()> {
     let foo = Foo { val: 123 };
     let name = CString::new("builtins.capsule").unwrap();

     let capsule = PyCapsule::new(py, foo, Some(name.clone()))?;

     let module = PyModule::import(py, "builtins")?;
     module.add("capsule", capsule)?;

     let cap: &Foo = unsafe { PyCapsule::import(py, name.as_ref())? };
     assert_eq!(cap.val, 123);
     Ok(())
 });
 assert!(r.is_ok());

Implementations

Constructs a new capsule whose contents are value, associated with name. name is the identifier for the capsule; if it is stored as an attribute of a module, the name should be in the format "modulename.attribute".

It is checked at compile time that the type T is not zero-sized. Rust function items need to be cast to a function pointer (fn(args) -> result) to be put into a capsule.

Example
use pyo3::{prelude::*, types::PyCapsule};
use std::ffi::CString;

Python::with_gil(|py| {
    let name = CString::new("foo").unwrap();
    let capsule = PyCapsule::new(py, 123_u32, Some(name)).unwrap();
    let val = unsafe { capsule.reference::<u32>() };
    assert_eq!(*val, 123);
});

However, attempting to construct a PyCapsule with a zero-sized type will not compile:

ⓘ
use pyo3::{prelude::*, types::PyCapsule};
use std::ffi::CString;

Python::with_gil(|py| {
    let capsule = PyCapsule::new(py, (), None).unwrap();  // Oops! `()` is zero sized!
});

Constructs a new capsule whose contents are value, associated with name.

Also provides a destructor: when the PyCapsule is destroyed, it will be passed the original object, as well as a *mut c_void which will point to the capsule’s context, if any.

The destructor must be Send, because there is no guarantee which thread it will eventually be called from.

Imports an existing capsule.

The name should match the path to the module attribute exactly in the form of "module.attribute", which should be the same as the name within the capsule.

Safety

It must be known that the capsule imported by name contains an item of type T.

Sets the context pointer in the capsule.

Returns an error if this capsule is not valid.

Notes

The context is treated much like the value of the capsule, but should likely act as a place to store any state management when using the capsule.

If you want to store a Rust value as the context, and drop it from the destructor, use Box::into_raw to convert it into a pointer, see the example.

Example
use std::sync::mpsc::{channel, Sender};
use libc::c_void;
use pyo3::{prelude::*, types::PyCapsule};

let (tx, rx) = channel::<String>();

fn destructor(val: u32, context: *mut c_void) {
    let ctx = unsafe { *Box::from_raw(context as *mut Sender<String>) };
    ctx.send("Destructor called!".to_string()).unwrap();
}

Python::with_gil(|py| {
    let capsule =
        PyCapsule::new_with_destructor(py, 123, None, destructor as fn(u32, *mut c_void))
            .unwrap();
    let context = Box::new(tx);  // `Sender<String>` is our context, box it up and ship it!
    capsule.set_context(Box::into_raw(context) as *mut c_void).unwrap();
    // This scope will end, causing our destructor to be called...
});

assert_eq!(rx.recv(), Ok("Destructor called!".to_string()));

Gets the current context stored in the capsule. If there is no context, the pointer will be null.

Returns an error if this capsule is not valid.

👎Deprecated since 0.17.0:

replaced with .context()

Deprecated form of .context().

Obtains a reference to the value of this capsule.

Safety

It must be known that this capsule is valid and its pointer is to an item of type T.

Gets the raw c_void pointer to the value in this capsule.

Returns null if this capsule is not valid.

Checks if this is a valid capsule.

Returns true if the stored pointer() is non-null.

Retrieves the name of this capsule, if set.

Returns an error if this capsule is not valid.

Methods from Deref<Target = PyAny>

Converts this PyAny to a concrete Python type.

Examples
use pyo3::prelude::*;
use pyo3::types::{PyAny, PyDict, PyList};

Python::with_gil(|py| {
    let dict = PyDict::new(py);
    assert!(dict.is_instance_of::<PyAny>().unwrap());
    let any: &PyAny = dict.as_ref();
    assert!(any.downcast::<PyDict>().is_ok());
    assert!(any.downcast::<PyList>().is_err());
});

Returns whether self and other point to the same object. To compare the equality of two objects (the == operator), use eq.

This is equivalent to the Python expression self is other.

Determines whether this object has the given attribute.

This is equivalent to the Python expression hasattr(self, attr_name).

To avoid repeated temporary allocations of Python strings, the intern! macro can be used to intern attr_name.

Retrieves an attribute value.

This is equivalent to the Python expression self.attr_name.

To avoid repeated temporary allocations of Python strings, the intern! macro can be used to intern attr_name.

Example: intern!ing the attribute name
#[pyfunction]
fn version(sys: &PyModule) -> PyResult<&PyAny> {
    sys.getattr(intern!(sys.py(), "version"))
}

Sets an attribute value.

This is equivalent to the Python expression self.attr_name = value.

To avoid repeated temporary allocations of Python strings, the intern! macro can be used to intern name.

Example: intern!ing the attribute name
#[pyfunction]
fn set_answer(ob: &PyAny) -> PyResult<()> {
    ob.setattr(intern!(ob.py(), "answer"), 42)
}

Deletes an attribute.

This is equivalent to the Python statement del self.attr_name.

To avoid repeated temporary allocations of Python strings, the intern! macro can be used to intern attr_name.

Returns an Ordering between self and other.

This is equivalent to the following Python code:

if self == other:
    return Equal
elif a < b:
    return Less
elif a > b:
    return Greater
else:
    raise TypeError("PyAny::compare(): All comparisons returned false")
Examples
use pyo3::prelude::*;
use pyo3::types::PyFloat;
use std::cmp::Ordering;

Python::with_gil(|py| -> PyResult<()> {
    let a = PyFloat::new(py, 0_f64);
    let b = PyFloat::new(py, 42_f64);
    assert_eq!(a.compare(b)?, Ordering::Less);
    Ok(())
})?;

It will return PyErr for values that cannot be compared:

use pyo3::prelude::*;
use pyo3::types::{PyFloat, PyString};

Python::with_gil(|py| -> PyResult<()> {
    let a = PyFloat::new(py, 0_f64);
    let b = PyString::new(py, "zero");
    assert!(a.compare(b).is_err());
    Ok(())
})?;

Tests whether two Python objects obey a given CompareOp.

lt, le, eq, ne, gt and ge are the specialized versions of this function.

Depending on the value of compare_op, this is equivalent to one of the following Python expressions:

compare_opPython expression
CompareOp::Eqself == other
CompareOp::Neself != other
CompareOp::Ltself < other
CompareOp::Leself <= other
CompareOp::Gtself > other
CompareOp::Geself >= other
Examples
use pyo3::class::basic::CompareOp;
use pyo3::prelude::*;
use pyo3::types::PyInt;

Python::with_gil(|py| -> PyResult<()> {
    let a: &PyInt = 0_u8.into_py(py).into_ref(py).downcast()?;
    let b: &PyInt = 42_u8.into_py(py).into_ref(py).downcast()?;
    assert!(a.rich_compare(b, CompareOp::Le)?.is_true()?);
    Ok(())
})?;

Tests whether this object is less than another.

This is equivalent to the Python expression self < other.

Tests whether this object is less than or equal to another.

This is equivalent to the Python expression self <= other.

Tests whether this object is equal to another.

This is equivalent to the Python expression self == other.

Tests whether this object is not equal to another.

This is equivalent to the Python expression self != other.

Tests whether this object is greater than another.

This is equivalent to the Python expression self > other.

Tests whether this object is greater than or equal to another.

This is equivalent to the Python expression self >= other.

Determines whether this object appears callable.

This is equivalent to Python’s callable() function.

Examples
use pyo3::prelude::*;

Python::with_gil(|py| -> PyResult<()> {
    let builtins = PyModule::import(py, "builtins")?;
    let print = builtins.getattr("print")?;
    assert!(print.is_callable());
    Ok(())
})?;

This is equivalent to the Python statement assert callable(print).

Note that unless an API needs to distinguish between callable and non-callable objects, there is no point in checking for callability. Instead, it is better to just do the call and handle potential exceptions.

Calls the object.

This is equivalent to the Python expression self(*args, **kwargs).

Examples
use pyo3::prelude::*;
use pyo3::types::PyDict;

const CODE: &str = r#"
def function(*args, **kwargs):
    assert args == ("hello",)
    assert kwargs == {"cruel": "world"}
    return "called with args and kwargs"
"#;

Python::with_gil(|py| {
    let module = PyModule::from_code(py, CODE, "", "")?;
    let fun = module.getattr("function")?;
    let args = ("hello",);
    let kwargs = PyDict::new(py);
    kwargs.set_item("cruel", "world")?;
    let result = fun.call(args, Some(kwargs))?;
    assert_eq!(result.extract::<&str>()?, "called with args and kwargs");
    Ok(())
})

Calls the object without arguments.

This is equivalent to the Python expression self().

Examples
use pyo3::prelude::*;

Python::with_gil(|py| -> PyResult<()> {
    let module = PyModule::import(py, "builtins")?;
    let help = module.getattr("help")?;
    help.call0()?;
    Ok(())
})?;

This is equivalent to the Python expression help().

Calls the object with only positional arguments.

This is equivalent to the Python expression self(*args).

Examples
use pyo3::prelude::*;

const CODE: &str = r#"
def function(*args, **kwargs):
    assert args == ("hello",)
    assert kwargs == {}
    return "called with args"
"#;

Python::with_gil(|py| {
    let module = PyModule::from_code(py, CODE, "", "")?;
    let fun = module.getattr("function")?;
    let args = ("hello",);
    let result = fun.call1(args)?;
    assert_eq!(result.extract::<&str>()?, "called with args");
    Ok(())
})

Calls a method on the object.

This is equivalent to the Python expression self.name(*args, **kwargs).

To avoid repeated temporary allocations of Python strings, the intern! macro can be used to intern name.

Examples
use pyo3::prelude::*;
use pyo3::types::PyDict;

const CODE: &str = r#"
class A:
    def method(self, *args, **kwargs):
        assert args == ("hello",)
        assert kwargs == {"cruel": "world"}
        return "called with args and kwargs"
a = A()
"#;

Python::with_gil(|py| {
    let module = PyModule::from_code(py, CODE, "", "")?;
    let instance = module.getattr("a")?;
    let args = ("hello",);
    let kwargs = PyDict::new(py);
    kwargs.set_item("cruel", "world")?;
    let result = instance.call_method("method", args, Some(kwargs))?;
    assert_eq!(result.extract::<&str>()?, "called with args and kwargs");
    Ok(())
})

Calls a method on the object without arguments.

This is equivalent to the Python expression self.name().

To avoid repeated temporary allocations of Python strings, the intern! macro can be used to intern name.

Examples
use pyo3::prelude::*;

const CODE: &str = r#"
class A:
    def method(self, *args, **kwargs):
        assert args == ()
        assert kwargs == {}
        return "called with no arguments"
a = A()
"#;

Python::with_gil(|py| {
    let module = PyModule::from_code(py, CODE, "", "")?;
    let instance = module.getattr("a")?;
    let result = instance.call_method0("method")?;
    assert_eq!(result.extract::<&str>()?, "called with no arguments");
    Ok(())
})

Calls a method on the object with only positional arguments.

This is equivalent to the Python expression self.name(*args).

To avoid repeated temporary allocations of Python strings, the intern! macro can be used to intern name.

Examples
use pyo3::prelude::*;

const CODE: &str = r#"
class A:
    def method(self, *args, **kwargs):
        assert args == ("hello",)
        assert kwargs == {}
        return "called with args"
a = A()
"#;

Python::with_gil(|py| {
    let module = PyModule::from_code(py, CODE, "", "")?;
    let instance = module.getattr("a")?;
    let args = ("hello",);
    let result = instance.call_method1("method", args)?;
    assert_eq!(result.extract::<&str>()?, "called with args");
    Ok(())
})

Returns whether the object is considered to be true.

This is equivalent to the Python expression bool(self).

Returns whether the object is considered to be None.

This is equivalent to the Python expression self is None.

Returns true if the sequence or mapping has a length of 0.

This is equivalent to the Python expression len(self) == 0.

Gets an item from the collection.

This is equivalent to the Python expression self[key].

Sets a collection item value.

This is equivalent to the Python expression self[key] = value.

Deletes an item from the collection.

This is equivalent to the Python expression del self[key].

Takes an object and returns an iterator for it.

This is typically a new iterator but if the argument is an iterator, this returns itself.

Returns the Python type object for this object’s type.

Returns the Python type pointer for this object.

Casts self to a concrete Python object type.

This can cast only to native Python types, not types implemented in Rust.

Extracts some type from the Python object.

This is a wrapper function around FromPyObject::extract().

Returns the reference count for the Python object.

Computes the “repr” representation of self.

This is equivalent to the Python expression repr(self).

Computes the “str” representation of self.

This is equivalent to the Python expression str(self).

Retrieves the hash code of self.

This is equivalent to the Python expression hash(self).

Returns the length of the sequence or mapping.

This is equivalent to the Python expression len(self).

Returns the list of attributes of this object.

This is equivalent to the Python expression dir(self).

Checks whether this object is an instance of type ty.

This is equivalent to the Python expression isinstance(self, ty).

Checks whether this object is an instance of type T.

This is equivalent to the Python expression isinstance(self, T), if the type T is known at compile time.

Determines if self contains value.

This is equivalent to the Python expression value in self.

Returns a GIL marker constrained to the lifetime of this type.

Available on non-PyPy only.

Return a proxy object that delegates method calls to a parent or sibling class of type.

This is equivalent to the Python expression super()

Trait Implementations

Gets the underlying FFI pointer, returns a borrowed pointer.

Converts this type into a shared reference of the (usually inferred) input type.

Formats the value using the given formatter. Read more

The resulting type after dereferencing.

Dereferences the value.

Formats the value using the given formatter. Read more

Converts to this type from the input type.

Converts to this type from the input type.

Extracts Self from the source PyObject.

Performs the conversion.

Returns a GIL marker constrained to the lifetime of this type.

Cast &PyAny to &Self without no type checking. Read more

Utility type to make Py::as_ref work.

Class name.

Module name, if any.

Returns the PyTypeObject instance for this type.

Checks if object is an instance of this type or a subclass of this type.

Returns the safe abstraction over the type object.

Checks if object is an instance of this type.

Converts self into a Python object.

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Convert from an arbitrary PyObject. Read more

Convert from an arbitrary borrowed PyObject. Read more

Convert from an arbitrary PyObject or panic. Read more

Convert from an arbitrary PyObject or panic. Read more

Convert from an arbitrary PyObject. Read more

Convert from an arbitrary borrowed PyObject. Read more

Convert from an arbitrary borrowed PyObject. Read more

Convert from an arbitrary borrowed PyObject. Read more

Calls U::from(self).

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

Cast from a concrete Python object type to PyObject.

Cast from a concrete Python object type to PyObject. With exact type check.

Cast a PyAny to a specific type of PyObject. The caller must have already verified the reference is for this type. Read more

👎Deprecated since 0.17.0:

this trait is no longer used by PyO3, use ToPyObject or IntoPy<PyObject>

Converts self into a Python object and calls the specified closure on the native FFI pointer underlying the Python object. Read more

Converts the given value to a String. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.