diff --git a/ortools/sat/python/cp_model.py b/ortools/sat/python/cp_model.py
index 7aa939da5f6..0a30abe38d0 100644
--- a/ortools/sat/python/cp_model.py
+++ b/ortools/sat/python/cp_model.py
@@ -612,7 +612,7 @@ def __str__(self):
         )
         if not exprs_str:
             return "0"
-        return exprs_str
+        return f"({exprs_str})"
 
     def __repr__(self):
         exprs_str = ", ".join(map(repr, self.__expressions))
@@ -757,7 +757,9 @@ def __str__(self) -> str:
     def __repr__(self) -> str:
         return "%s(%s)" % (self.__var.name, DisplayBounds(self.__var.domain))
 
-    def Name(self) -> Optional[str]:
+    def Name(self) -> str:
+        if not self.__var or not self.__var.name:
+            return ""
         return self.__var.name
 
     def Not(self) -> "_NotBooleanVariable":
@@ -946,6 +948,8 @@ def WithName(self, name: str) -> "Constraint":
 
     def Name(self) -> str:
         """Returns the name of the constraint."""
+        if not self.__constraint or not self.__constraint.name:
+            return ""
         return self.__constraint.name
 
     def Index(self) -> int:
@@ -1036,6 +1040,8 @@ def __repr__(self):
             )
 
     def Name(self) -> str:
+        if not self.__ct or not self.__ct.name:
+            return ""
         return self.__ct.name
 
     def StartExpr(self) -> LinearExprT:
@@ -1096,6 +1102,8 @@ def __init__(self):
     # Naming.
     def Name(self) -> str:
         """Returns the name of the model."""
+        if not self.__model or not self.__model.name:
+            return ""
         return self.__model.name
 
     def SetName(self, name: str):
diff --git a/ortools/sat/python/cp_model_test.py b/ortools/sat/python/cp_model_test.py
index 328cd5a7644..825cbababba 100644
--- a/ortools/sat/python/cp_model_test.py
+++ b/ortools/sat/python/cp_model_test.py
@@ -13,8 +13,9 @@
 # limitations under the License.
 
 """Tests for ortools.sat.python.cp_model."""
-
 from absl.testing import absltest
+import pandas as pd
+
 from ortools.sat.python import cp_model
 
 
@@ -61,7 +62,7 @@ def Obj(self):
         return self.__obj
 
 
-class LogToString(object):
+class LogToString:
     """Record log in a string."""
 
     def __init__(self):
@@ -473,7 +474,7 @@ def testWeightedSum(self):
         print("testWeightedSum")
         model = cp_model.CpModel()
         x = [model.NewIntVar(0, 2, "x%i" % i) for i in range(100)]
-        c = [2 for i in range(100)]
+        c = [2] * 100
         model.Add(cp_model.LinearExpr.WeightedSum(x, c) <= 3)
         model.Maximize(x[99])
         solver = cp_model.CpSolver()
@@ -1089,8 +1090,7 @@ def testDisplayBounds(self):
     def testShortName(self):
         print("testShortName")
         model = cp_model.CpModel()
-        v = model.Proto().variables.add()
-        v.domain.extend([5, 10])
+        model.Proto().variables.add(domain=[5, 10])
         self.assertEqual("[5..10]", cp_model.ShortName(model.Proto(), 0))
 
     def testIntegerExpressionErrors(self):
@@ -1420,6 +1420,30 @@ def testModelError(self):
         self.assertEqual(cp_model.MODEL_INVALID, solver.Solve(model))
         self.assertEqual(solver.SolutionInfo(), 'var #0 has no domain(): name: "x0"')
 
+    def testIntVarSeries(self):
+        print("testIntVarSeries")
+        df = pd.DataFrame([1, -1, 1], columns=["coeffs"])
+        model = cp_model.CpModel()
+        x = model.NewIntVarSeries(
+            name="x", index=df.index, lower_bounds=0, upper_bounds=5
+        )
+        model.Minimize(df.coeffs.dot(x))
+        solver = cp_model.CpSolver()
+        self.assertEqual(cp_model.OPTIMAL, solver.Solve(model))
+        solution = solver.Values(x)
+        self.assertTrue((solution.values == [0, 5, 0]).all())
+
+    def testBoolVarSeries(self):
+        print("testBoolVarSeries")
+        df = pd.DataFrame([1, -1, 1], columns=["coeffs"])
+        model = cp_model.CpModel()
+        x = model.NewBoolVarSeries(name="x", index=df.index)
+        model.Minimize(df.coeffs.dot(x))
+        solver = cp_model.CpSolver()
+        self.assertEqual(cp_model.OPTIMAL, solver.Solve(model))
+        solution = solver.BooleanValues(x)
+        self.assertTrue((solution.values == [False, True, False]).all())
+
 
 if __name__ == "__main__":
     absltest.main()