Remove explicit object superclass (#2910)

cirq/circuits/insert_strategy.py

@@ -15,7 +15,7 @@
 """Hard-coded options for adding multiple operations to a circuit."""
 
 
-class InsertStrategy(object):
+class InsertStrategy:
     """Indicates preferences on how to add multiple operations to a circuit."""
 
     NEW = None  # type: InsertStrategy

cirq/contrib/qasm_import/_lexer.py

@@ -20,7 +20,7 @@
 from cirq.contrib.qasm_import.exception import QasmException
 
 
-class QasmLexer(object):
+class QasmLexer:
 
     def __init__(self):
         self.lex = lex.lex(object=self, debug=False)
@@ -111,8 +111,8 @@ def t_COMMENT(self, t):
         r"""//.*"""
 
     def t_error(self, t):
-        raise QasmException("Illegal character '{}' at line {}".format(
-            t.value[0], t.lineno))
+        raise QasmException(
+            f"Illegal character '{t.value[0]}' at line {t.lineno}")
 
     def input(self, qasm):
         self.lex.input(qasm)

cirq/google/line/placement/anneal.py

@@ -35,9 +35,8 @@
 _STATE = Tuple[List[List[GridQubit]], Set[EDGE]]
 
 
-class AnnealSequenceSearch(object):
-    """Simulated annealing search heuristic.
-    """
+class AnnealSequenceSearch:
+    """Simulated annealing search heuristic."""
 
     def __init__(self, device: 'cirq.google.XmonDevice', seed=None) -> None:
         """Greedy sequence search constructor.

cirq/study/resolver.py

@@ -34,7 +34,7 @@
     """Something that can be used to turn parameters into values.""")
 
 
-class ParamResolver(object):
+class ParamResolver:
     """Resolves sympy.Symbols to actual values.
 
     A Symbol is a wrapped parameter name (str). A ParamResolver is an object