[英]How to pass a Rust function as a callback to Python using pyo3
我正在使用 Pyo3 從 Python 調用 Rust 函數,反之亦然。
我正在努力實現以下目標:
Python 調用rust_function_1
Rust function rust_function_1
調用 Python function python_function
傳遞 Rust function rust_function_2
作為回調參數
Python function python_function
調用回調,在本例中為 Rust function rust_function_2
我不知道如何將rust_function_2
作為回調參數傳遞給python_function
。
我有以下 Python 代碼:
import rust_module
def python_function(callback):
print("This is python_function")
callback()
if __name__ == '__main__':
rust_module.rust_function_1()
我有以下非編譯 Rust 代碼:
use pyo3::prelude::*;
#[pyfunction]
fn rust_function_1() -> PyResult<()> {
println!("This is rust_function_1");
Python::with_gil(|py| {
let python_module = PyModule::import(py, "python_module")?;
python_module
.getattr("python_function")?
.call1((rust_function_2.into_py(py),))?; // Compile error
Ok(())
})
}
#[pyfunction]
fn rust_function_2() -> PyResult<()> {
println!("This is rust_function_2");
Ok(())
}
#[pymodule]
#[pyo3(name = "rust_module")]
fn quantum_network_stack(_python: Python, module: &PyModule) -> PyResult<()> {
module.add_function(wrap_pyfunction!(rust_function_1, module)?)?;
module.add_function(wrap_pyfunction!(rust_function_2, module)?)?;
Ok(())
}
錯誤信息是:
error[E0599]: the method `into_py` exists for fn item `fn() -> Result<(), PyErr> {rust_function_2}`, but its trait bounds were not satisfied
--> src/lib.rs:10:37
|
10 | .call1((rust_function_2.into_py(py),))?;
| ^^^^^^^ method cannot be called on `fn() -> Result<(), PyErr> {rust_function_2}` due to unsatisfied trait bounds
|
= note: `rust_function_2` is a function, perhaps you wish to call it
= note: the following trait bounds were not satisfied:
`fn() -> Result<(), PyErr> {rust_function_2}: AsPyPointer`
which is required by `&fn() -> Result<(), PyErr> {rust_function_2}: pyo3::IntoPy<Py<PyAny>>`
PitaJ 的評論讓我找到了解決方案。
有效的 Rust 代碼:
use pyo3::prelude::*;
#[pyclass]
struct Callback {
#[allow(dead_code)] // callback_function is called from Python
callback_function: fn() -> PyResult<()>,
}
#[pymethods]
impl Callback {
fn __call__(&self) -> PyResult<()> {
(self.callback_function)()
}
}
#[pyfunction]
fn rust_function_1() -> PyResult<()> {
println!("This is rust_function_1");
Python::with_gil(|py| {
let python_module = PyModule::import(py, "python_module")?;
let callback = Box::new(Callback {
callback_function: rust_function_2,
});
python_module
.getattr("python_function")?
.call1((callback.into_py(py),))?;
Ok(())
})
}
#[pyfunction]
fn rust_function_2() -> PyResult<()> {
println!("This is rust_function_2");
Ok(())
}
#[pymodule]
#[pyo3(name = "rust_module")]
fn quantum_network_stack(_python: Python, module: &PyModule) -> PyResult<()> {
module.add_function(wrap_pyfunction!(rust_function_1, module)?)?;
module.add_function(wrap_pyfunction!(rust_function_2, module)?)?;
module.add_class::<Callback>()?;
Ok(())
}
Python 有效的代碼(與問題相同):
import rust_module
def python_function(callback):
print("This is python_function")
callback()
if __name__ == '__main__':
rust_module.rust_function_1()
以下解決方案以多種方式改進了上述解決方案:
Rust 提供的callback
被存儲並稍后調用,而不是立即被調用(這對於現實生活用例更現實)
每次當 Python 調用 Rust 時,它都會傳入一個PythonApi
object,這樣就無需在每次調用時對 Rust function 進行 Python import
。
Rust 提供的回調除了普通函數外,還可以是捕獲變量(僅移動語義)的閉包。
比較通用的Rust代碼如下:
use pyo3::prelude::*;
#[pyclass]
struct Callback {
#[allow(dead_code)] // callback_function is called from Python
callback_function: Box<dyn Fn(&PyAny) -> PyResult<()> + Send>,
}
#[pymethods]
impl Callback {
fn __call__(&self, python_api: &PyAny) -> PyResult<()> {
(self.callback_function)(python_api)
}
}
#[pyfunction]
fn rust_register_callback(python_api: &PyAny) -> PyResult<()> {
println!("This is rust_register_callback");
let message: String = "a captured variable".to_string();
Python::with_gil(|py| {
let callback = Box::new(Callback {
callback_function: Box::new(move |python_api| {
rust_callback(python_api, message.clone())
}),
});
python_api
.getattr("set_callback")?
.call1((callback.into_py(py),))?;
Ok(())
})
}
#[pyfunction]
fn rust_callback(python_api: &PyAny, message: String) -> PyResult<()> {
println!("This is rust_callback");
println!("Message = {}", message);
python_api.getattr("some_operation")?.call0()?;
Ok(())
}
#[pymodule]
#[pyo3(name = "rust_module")]
fn quantum_network_stack(_python: Python, module: &PyModule) -> PyResult<()> {
module.add_function(wrap_pyfunction!(rust_register_callback, module)?)?;
module.add_function(wrap_pyfunction!(rust_callback, module)?)?;
module.add_class::<Callback>()?;
Ok(())
}
比較通用的Python代碼如下:
import rust_module
class PythonApi:
def __init__(self):
self.callback = None
def set_callback(self, callback):
print("This is PythonApi::set_callback")
self.callback = callback
def call_callback(self):
print("This is PythonApi::call_callback")
assert self.callback is not None
self.callback(self)
def some_operation(self):
print("This is PythonApi::some_operation")
def python_function(python_api, callback):
print("This is python_function")
python_api.callback = callback
def main():
print("This is main")
python_api = PythonApi()
print("Calling rust_register_callback")
rust_module.rust_register_callback(python_api)
print("Returned from rust_register_callback; back in main")
print("Calling callback")
python_api.call_callback()
if __name__ == '__main__':
main()
后一版代碼中的output如下:
This is main
Calling rust_register_callback
This is rust_register_callback
This is PythonApi::set_callback
Returned from rust_register_callback; back in main
Calling callback
This is PythonApi::call_callback
This is rust_callback
Message = a captured variable
This is PythonApi::some_operation
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