use std::collections::HashMap; use pyo3::exceptions::PyKeyError; use pyo3::prelude::*; use pyo3::types::IntoPyDict; use pyo3::types::PyList; use pyo3::PyMappingProtocol; #[pyclass] struct Mapping { index: HashMap, } #[pymethods] impl Mapping { #[new] fn new(elements: Option<&PyList>) -> PyResult { if let Some(pylist) = elements { let mut elems = HashMap::with_capacity(pylist.len()); for (i, pyelem) in pylist.into_iter().enumerate() { let elem = String::extract(pyelem)?; elems.insert(elem, i); } Ok(Self { index: elems }) } else { Ok(Self { index: HashMap::new(), }) } } } #[pyproto] impl PyMappingProtocol for Mapping { fn __len__(&self) -> usize { self.index.len() } fn __getitem__(&self, query: String) -> PyResult { self.index .get(&query) .copied() .ok_or_else(|| PyKeyError::new_err("unknown key")) } fn __setitem__(&mut self, key: String, value: usize) { self.index.insert(key, value); } fn __delitem__(&mut self, key: String) -> PyResult<()> { if self.index.remove(&key).is_none() { Err(PyKeyError::new_err("unknown key")) } else { Ok(()) } } /// not an actual reversed implementation, just to demonstrate that the method is callable. fn __reversed__(&self) -> PyObject { let gil = Python::acquire_gil(); self.index .keys() .cloned() .collect::>() .into_py(gil.python()) } } #[test] fn test_getitem() { let gil = Python::acquire_gil(); let py = gil.python(); let d = [("Mapping", py.get_type::())].into_py_dict(py); let run = |code| py.run(code, None, Some(d)).unwrap(); let err = |code| py.run(code, None, Some(d)).unwrap_err(); run("m = Mapping(['1', '2', '3']); assert m['1'] == 0"); run("m = Mapping(['1', '2', '3']); assert m['2'] == 1"); run("m = Mapping(['1', '2', '3']); assert m['3'] == 2"); err("m = Mapping(['1', '2', '3']); print(m['4'])"); } #[test] fn test_setitem() { let gil = Python::acquire_gil(); let py = gil.python(); let d = [("Mapping", py.get_type::())].into_py_dict(py); let run = |code| py.run(code, None, Some(d)).unwrap(); let err = |code| py.run(code, None, Some(d)).unwrap_err(); run("m = Mapping(['1', '2', '3']); m['1'] = 4; assert m['1'] == 4"); run("m = Mapping(['1', '2', '3']); m['0'] = 0; assert m['0'] == 0"); run("m = Mapping(['1', '2', '3']); len(m) == 4"); err("m = Mapping(['1', '2', '3']); m[0] = 'hello'"); err("m = Mapping(['1', '2', '3']); m[0] = -1"); } #[test] fn test_delitem() { let gil = Python::acquire_gil(); let py = gil.python(); let d = [("Mapping", py.get_type::())].into_py_dict(py); let run = |code| py.run(code, None, Some(d)).unwrap(); let err = |code| py.run(code, None, Some(d)).unwrap_err(); run( "m = Mapping(['1', '2', '3']); del m['1']; assert len(m) == 2; \ assert m['2'] == 1; assert m['3'] == 2", ); err("m = Mapping(['1', '2', '3']); del m[-1]"); err("m = Mapping(['1', '2', '3']); del m['4']"); } #[test] fn test_reversed() { let gil = Python::acquire_gil(); let py = gil.python(); let d = [("Mapping", py.get_type::())].into_py_dict(py); let run = |code| py.run(code, None, Some(d)).unwrap(); run("m = Mapping(['1', '2']); assert set(reversed(m)) == {'1', '2'}"); }