Improve __str__ and __repr__ for SingleQubitCliffordGate (issue #6326) (#6920)

Change __repr__ to be simpler following the recommendation in the issue description.

Author: codrut3

cirq-core/cirq/ops/clifford_gate.py

@@ -897,7 +897,12 @@ def equivalent_gate_before(self, after: 'SingleQubitCliffordGate') -> 'SingleQub
         return self.merged_with(after).merged_with(self**-1)
 
     def __repr__(self) -> str:
-        return f'cirq.CliffordGate.from_clifford_tableau({self.clifford_tableau!r})'
+        return (
+            f'cirq.ops.SingleQubitCliffordGate(_clifford_tableau=cirq.CliffordTableau(1, '
+            f'rs=np.array({self._clifford_tableau.rs.tolist()!r}), '
+            f'xs=np.array({self._clifford_tableau.xs.tolist()!r}), '
+            f'zs=np.array({self._clifford_tableau.zs.tolist()!r})))'
+        )
 
     def _circuit_diagram_info_(
         self, args: 'cirq.CircuitDiagramInfoArgs'

cirq-core/cirq/ops/clifford_gate_test.py

@@ -919,3 +919,37 @@ def test_all_single_qubit_clifford_unitaries():
     assert cirq.equal_up_to_global_phase(cs[21], (i - 1j * (-x + y - z)) / 2)
     assert cirq.equal_up_to_global_phase(cs[22], (i - 1j * (-x - y + z)) / 2)
     assert cirq.equal_up_to_global_phase(cs[23], (i - 1j * (-x - y - z)) / 2)
+
+
+def test_single_qubit_clifford_gate_repr():
+    assert repr(cirq.ops.SingleQubitCliffordGate.X) == (
+        'cirq.ops.SingleQubitCliffordGate(_clifford_tableau=cirq.CliffordTableau(1, '
+        'rs=np.array([False, True]), xs=np.array([[True], [False]]), '
+        'zs=np.array([[False], [True]])))'
+    )
+    assert repr(cirq.ops.SingleQubitCliffordGate.Y) == (
+        'cirq.ops.SingleQubitCliffordGate(_clifford_tableau=cirq.CliffordTableau(1, '
+        'rs=np.array([True, True]), xs=np.array([[True], [False]]), '
+        'zs=np.array([[False], [True]])))'
+    )
+    assert repr(cirq.ops.SingleQubitCliffordGate.Z) == (
+        'cirq.ops.SingleQubitCliffordGate(_clifford_tableau=cirq.CliffordTableau(1, '
+        'rs=np.array([True, False]), xs=np.array([[True], [False]]), '
+        'zs=np.array([[False], [True]])))'
+    )
+    assert repr(cirq.ops.SingleQubitCliffordGate.I) == (
+        'cirq.ops.SingleQubitCliffordGate(_clifford_tableau=cirq.CliffordTableau(1, '
+        'rs=np.array([False, False]), xs=np.array([[True], [False]]), '
+        'zs=np.array([[False], [True]])))'
+    )
+    assert repr(cirq.ops.SingleQubitCliffordGate.X_sqrt) == (
+        'cirq.ops.SingleQubitCliffordGate(_clifford_tableau=cirq.CliffordTableau(1, '
+        'rs=np.array([False, True]), xs=np.array([[True], [True]]), '
+        'zs=np.array([[False], [True]])))'
+    )
+
+    assert str(cirq.ops.SingleQubitCliffordGate.X) == (
+        'cirq.ops.SingleQubitCliffordGate(_clifford_tableau=cirq.CliffordTableau(1, '
+        'rs=np.array([False, True]), xs=np.array([[True], [False]]), '
+        'zs=np.array([[False], [True]])))'
+    )