Add constant property to SymbolicOperator (#423)

* add constant property to SymbolicOperator * add test
quantumlib · Aug 6, 2018 · c1c3c5b · c1c3c5b
1 parent 9cbe5d4
commit c1c3c5b
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Showing 3 changed files with 14 additions and 2 deletions.
diff --git a/src/openfermion/ops/_polynomial_tensor.py b/src/openfermion/ops/_polynomial_tensor.py
@@ -137,8 +137,8 @@ def __init__(self, n_body_tensors):
 
     @property
     def constant(self):
-        """Get the value of the constant term."""
-        return self.n_body_tensors.get((), 0.)
+        """The value of the constant term."""
+        return self.n_body_tensors.get((), 0.0)
 
     @constant.setter
     def constant(self, value):

diff --git a/src/openfermion/ops/_symbolic_operator.py b/src/openfermion/ops/_symbolic_operator.py
@@ -273,6 +273,11 @@ def _parse_string(self, term):
         # Return a tuple
         return tuple(processed_term)
 
+    @property
+    def constant(self):
+        """The value of the constant term."""
+        return self.terms.get((), 0.0)
+
     @classmethod
     def zero(cls):
         """

diff --git a/src/openfermion/ops/_symbolic_operator_test.py b/src/openfermion/ops/_symbolic_operator_test.py
@@ -77,6 +77,13 @@ def test_symbolic_operator_is_abstract_cant_instantiate(self):
         with self.assertRaises(TypeError):
             _ = SymbolicOperator()
 
+    def test_symbolic_operator_constant(self):
+        op = DummyOperator1((), 1.723)
+        self.assertEqual(op.constant, 1.723)
+
+        op = DummyOperator1('1^ 4', 0.182)
+        self.assertEqual(op.constant, 0.0)
+
     def test_init_single_factor(self):
         """Test initialization of the form DummyOperator((index, action))."""
         equals_tester = EqualsTester(self)