pylint - enforce singleton-comparison check (quantumlib#4625)

Correct few lint issues that show after enabling singleton-comparison check.

cirq-core/cirq/_compat_test.py

@@ -455,7 +455,7 @@ def _import_parent_use_constant_from_deprecated_module_attribute():
     # the parent should have fake_a set on it as an attribute - just like
     # a regular module import (e.g. cirq.ops)
     # should have a DUPE_CONSTANT as its imported from the dupe submodule
-    assert cirq.testing._compat_test_data.fake_a.DUPE_CONSTANT == False
+    assert cirq.testing._compat_test_data.fake_a.DUPE_CONSTANT is False
 
     assert 'module_a for module deprecation tests' in cirq.testing._compat_test_data.fake_a.__doc__
     assert 'Test module for deprecation testing' in cirq.testing._compat_test_data.__doc__
@@ -467,7 +467,7 @@ def _import_deprecated_sub_use_constant():
     import cirq.testing._compat_test_data.fake_a.dupe  # type: ignore
 
     # should have a DUPE_CONSTANT as its defined on it, set to False
-    assert cirq.testing._compat_test_data.fake_a.dupe.DUPE_CONSTANT == False
+    assert cirq.testing._compat_test_data.fake_a.dupe.DUPE_CONSTANT is False
 
 
 def _import_deprecated_same_name_in_earlier_subtree():

cirq-core/cirq/circuits/qasm_output.py

@@ -222,7 +222,7 @@ def _generate_qubit_ids(self) -> Dict['cirq.Qid', str]:
 
     def is_valid_qasm_id(self, id_str: str) -> bool:
         """Test if id_str is a valid id in QASM grammar."""
-        return self.valid_id_re.match(id_str) != None
+        return self.valid_id_re.match(id_str) is not None
 
     def save(self, path: Union[str, bytes, int]) -> None:
         """Write QASM output to a file specified by path."""

cirq-core/cirq/contrib/graph_device/uniform_graph_device_test.py

@@ -42,5 +42,5 @@ def test_regular_uniform_undirected_linear_device(arity):
     assert device.qubits == tuple(cirq.LineQubit.range(n_qubits))
     assert len(device.edges) == n_qubits - arity + 1
     for edge, label in device.labelled_edges.items():
-        assert label == None
+        assert label is None
         assert len(edge) == arity

cirq-core/cirq/ion/ion_gates_test.py

@@ -77,4 +77,4 @@ def custom_resolver(cirq_type: str) -> Union[Callable[..., cirq.Gate], None]:
     assert cirq.read_json(
         json_text=cirq.to_json(cirq.ms(np.pi / 2)), resolvers=[custom_resolver]
     ) == cirq.ms(np.pi / 2)
-    assert custom_resolver('X') == None
+    assert custom_resolver('X') is None

cirq-core/cirq/ops/measurement_gate_test.py

@@ -156,7 +156,7 @@ def test_qudit_measure_quil():
             cirq.measure(q0, key='a'),
             formatter=cirq.QuilFormatter(qubit_id_map=qubit_id_map, measurement_id_map={}),
         )
-        == None
+        is None
     )
 
 

cirq-core/cirq/protocols/apply_channel_protocol.py

@@ -235,9 +235,8 @@ def apply_channel(
         )
 
     # Check if the specialized method is present.
-    func = getattr(val, '_apply_channel_', None)
-    if func is not None:
-        result = func(args)
+    if hasattr(val, '_apply_channel_'):
+        result = val._apply_channel_(args)
         if result is not NotImplemented and result is not None:
 
             def err_str(buf_num_str):

cirq-core/cirq/protocols/apply_mixture_protocol.py

@@ -239,9 +239,8 @@ def apply_mixture(
     val, args, is_density_matrix = _validate_input(val, args)
 
     # Check if the specialized method is present. (STEP A)
-    func = getattr(val, '_apply_mixture_', None)
-    if func is not None:
-        result = func(args)
+    if hasattr(val, '_apply_mixture_'):
+        result = val._apply_mixture_(args)
         if result is not NotImplemented and result is not None:
 
             def err_str(buf_num_str):

cirq-core/cirq/protocols/phase_protocol_test.py

@@ -47,8 +47,8 @@ def _phase_by_(self, phase_turns, qubit_on):
         _ = cirq.phase_by(rin, 1, 0)
 
     # With default
-    assert cirq.phase_by(n, 1, 0, default=None) == None
-    assert cirq.phase_by(rin, 1, 0, default=None) == None
+    assert cirq.phase_by(n, 1, 0, default=None) is None
+    assert cirq.phase_by(rin, 1, 0, default=None) is None
 
     test = PhaseIsAddition(3)
     assert test.phase == [0, 0, 0]

cirq-core/cirq/qis/clifford_tableau_test.py

@@ -197,7 +197,7 @@ def test_validate_tableau():
     assert t._validate()
 
     t.xs = np.zeros((4, 2))
-    assert t._validate() == False
+    assert not t._validate()
 
 
 def test_rowsum():

cirq-google/cirq_google/engine/engine_client.py

@@ -868,7 +868,7 @@ def update_reservation(
         if end:
             reservation.end_time.seconds = int(end.timestamp())
             paths.append('end_time')
-        if whitelisted_users != None:
+        if whitelisted_users is not None:
             reservation.whitelisted_users.extend(whitelisted_users)
             paths.append('whitelisted_users')
 

cirq-google/cirq_google/engine/engine_client_test.py

@@ -1028,7 +1028,7 @@ def test_get_reservation_not_found(client_constructor):
 
     client = EngineClient()
     assert (client.get_reservation('proj', 'processor0',
-                                   'papar-party-44') == None)
+                                   'papar-party-44') is None)
     kwargs = grpc_client.get_quantum_reservation.call_args[1]
     assert kwargs == {
         'name': name,

cirq-ionq/cirq_ionq/ionq_client_test.py

@@ -85,7 +85,7 @@ def test_ionq_client_attributes():
     }
     assert client.default_target == 'qpu'
     assert client.max_retry_seconds == 10
-    assert client.verbose == True
+    assert client.verbose is True
 
 
 @mock.patch('requests.post')

dev_tools/conf/.pylintrc

@@ -40,6 +40,7 @@ enable=
     return-in-init,
     return-outside-function,
     simplifiable-if-statement,
+    singleton-comparison,
     syntax-error,
     too-many-function-args,
     trailing-whitespace,

dev_tools/snippets_test.py

@@ -500,7 +500,7 @@ def print_capture(*values, sep=' '):
         assert_expected_lines_present_in_order(expected_outputs, output_lines)
     except AssertionError as ex:
         new_msg = ex.args[0] + '\n\nIn snippet{}:\n{}'.format(
-            "" if line_number == None else " (line {})".format(line_number), _indent([snippet])
+            "" if line_number is None else " (line {})".format(line_number), _indent([snippet])
         )
         ex.args = (new_msg,) + tuple(ex.args[1:])
         raise