Fix: Hide all private attributes in Target

- Hide all private attributes of the `Target` to prevent unecessary cloning.
- Other small tweaks and fixes.

crates/accelerate/src/target.rs

@@ -37,30 +37,59 @@ struct Qargs {
 
 impl IntoPy<PyObject> for Qargs {
     fn into_py(self, py: Python<'_>) -> PyObject {
-        if self.vec.len() == 1 {
-            let qargs: (PhysicalQubit,) = self.vec.into_iter().collect_tuple().unwrap();
-            qargs.to_object(py)
-        } else if self.vec.len() == 2 {
-            let qargs: (PhysicalQubit, PhysicalQubit) =
-                self.vec.into_iter().collect_tuple().unwrap();
-            qargs.to_object(py)
-        } else if self.vec.len() == 3 {
-            let qargs: (PhysicalQubit, PhysicalQubit, PhysicalQubit) =
-                self.vec.into_iter().collect_tuple().unwrap();
-            qargs.to_object(py)
-        } else if self.vec.len() == 4 {
-            let qargs: (PhysicalQubit, PhysicalQubit, PhysicalQubit, PhysicalQubit) =
-                self.vec.into_iter().collect_tuple().unwrap();
-            qargs.to_object(py)
-        } else {
-            py.None()
+        match self.vec.len() {
+            1 => {
+                let qargs: (PhysicalQubit,) = self.vec.into_iter().collect_tuple().unwrap();
+                qargs.to_object(py)
+            }
+            2 => {
+                let qargs: (PhysicalQubit, PhysicalQubit) =
+                    self.vec.into_iter().collect_tuple().unwrap();
+                qargs.to_object(py)
+            }
+            3 => {
+                let qargs: (PhysicalQubit, PhysicalQubit, PhysicalQubit) =
+                    self.vec.into_iter().collect_tuple().unwrap();
+                qargs.to_object(py)
+            }
+            4 => {
+                let qargs: (PhysicalQubit, PhysicalQubit, PhysicalQubit, PhysicalQubit) =
+                    self.vec.into_iter().collect_tuple().unwrap();
+                qargs.to_object(py)
+            }
+            _ => py.None(),
         }
     }
 }
 
 impl ToPyObject for Qargs {
     fn to_object(&self, py: Python<'_>) -> PyObject {
-        self.clone().into_py(py)
+        match self.vec.len() {
+            1 => {
+                let qargs: (&PhysicalQubit,) = self.vec.iter().collect_tuple().unwrap();
+                qargs.to_object(py)
+            }
+            2 => {
+                let qargs: (&PhysicalQubit, &PhysicalQubit) =
+                    self.vec.iter().collect_tuple().unwrap();
+                qargs.to_object(py)
+            }
+            3 => {
+                let qargs: (&PhysicalQubit, &PhysicalQubit, &PhysicalQubit) =
+                    self.vec.iter().collect_tuple().unwrap();
+                qargs.to_object(py)
+            }
+            4 => {
+                let qargs: (
+                    &PhysicalQubit,
+                    &PhysicalQubit,
+                    &PhysicalQubit,
+                    &PhysicalQubit,
+                ) = self.vec.iter().collect_tuple().unwrap();
+                qargs.to_object(py)
+            }
+            _ => py.None(),
+        }
     }
 }
 
@@ -392,14 +421,10 @@ pub struct Target {
     #[pyo3(get, set)]
     pub concurrent_measurements: Vec<Vec<usize>>,
     // Maybe convert PyObjects into rust representations of Instruction and Data
-    #[pyo3(get)]
     gate_map: GateMapType,
-    #[pyo3(get)]
     gate_name_map: IndexMap<String, PyObject>,
     global_operations: IndexMap<usize, HashSet<String>>,
-    #[pyo3(get)]
     qarg_gate_map: IndexMap<Option<Qargs>, Option<HashSet<String>>>,
-    #[pyo3(get, set)]
     instruction_durations: Option<PyObject>,
     instruction_schedule_map: Option<PyObject>,
     #[pyo3(get, set)]
@@ -1048,9 +1073,9 @@ impl Target {
         operations.
     */
     #[pyo3(text_signature = "(instruction, /)")]
-    fn operation_from_name(&self, instruction: String) -> PyResult<PyObject> {
-        if self.gate_name_map.contains_key(&instruction) {
-            Ok(self.gate_name_map[&instruction].to_owned())
+    fn operation_from_name(&self, py: Python<'_>, instruction: String) -> PyResult<PyObject> {
+        if let Some(gate_obj) = self.gate_name_map.get(&instruction) {
+            Ok(gate_obj.to_object(py))
         } else {
             Err(PyKeyError::new_err(format!(
                 "Instruction {:?} not in target",
@@ -2088,9 +2113,8 @@ impl Target {
     }
 
     fn __getitem__(&self, py: Python<'_>, key: String) -> PyResult<PyObject> {
-        if self.gate_map.contains_key(&key) {
-            let value = &self.gate_map[&key];
-            Ok(value.to_object(py))
+        if let Some(qarg_instprop) = self.gate_map.get(&key) {
+            Ok(qarg_instprop.to_object(py))
         } else {
             Err(PyKeyError::new_err(format!("{key} not in gate_map")))
         }

qiskit/transpiler/target.py

@@ -228,15 +228,15 @@ def _build_coupling_graph(self):
             multigraph=False
         )
         self.coupling_graph.add_nodes_from([{} for _ in range(self.num_qubits)])
-        for gate, qarg_map in self.gate_map.items():
+        for gate, qarg_map in self.items():
             if qarg_map is None:
                 if self.gate_name_map[gate].num_qubits == 2:
                     self.coupling_graph = None  # pylint: disable=attribute-defined-outside-init
                     return
                 continue
             for qarg, properties in qarg_map.items():
                 if qarg is None:
-                    if self.gate_name_map[gate].num_qubits == 2:
+                    if self.operation_from_name(gate).num_qubits == 2:
                         self.coupling_graph = None  # pylint: disable=attribute-defined-outside-init
                         return
                     continue
@@ -250,7 +250,10 @@ def _build_coupling_graph(self):
                         edge_data[gate] = properties
                     except rx.NoEdgeBetweenNodes:
                         self.coupling_graph.add_edge(*qarg, {gate: properties})
-        if self.coupling_graph.num_edges() == 0 and any(x is None for x in self.qarg_gate_map):
+        qargs = self.qargs
+        if self.coupling_graph.num_edges() == 0 and (
+            qargs == None or any(x is None for x in qargs)
+        ):
             self.coupling_graph = None  # pylint: disable=attribute-defined-outside-init
 
     def build_coupling_map(self, two_q_gate=None, filter_idle_qubits=False):
@@ -298,7 +301,7 @@ def build_coupling_map(self, two_q_gate=None, filter_idle_qubits=False):
         if two_q_gate is not None:
             coupling_graph = rx.PyDiGraph(multigraph=False)
             coupling_graph.add_nodes_from([None] * self.num_qubits)
-            for qargs, properties in self.gate_map[two_q_gate].items():
+            for qargs, properties in self[two_q_gate].items():
                 if len(qargs) != 2:
                     raise ValueError(
                         "Specified two_q_gate: %s is not a 2 qubit instruction" % two_q_gate
@@ -339,10 +342,6 @@ def keys(self):
         """Return all gate names present in the Target"""
         return {x: None for x in super().keys()}.keys()
 
-    def items(self):
-        """Returns a map of all qargs and properties for each gate."""
-        return super().gate_map.items()
-
     def __str__(self):
         output = io.StringIO()
         if self.description is not None: