Fix 128 (Initialization with multi term FermionicOp) (#131) (#137)

* fix 128 * add release note Co-authored-by: Manoel Marques <[email protected]> Co-authored-by: Steve Wood <[email protected]> (cherry picked from commit 625939e) Co-authored-by: Ikko Hamamura <[email protected]>
qiskit-community · Apr 14, 2021 · f5a59c7 · f5a59c7
1 parent ab48066
commit f5a59c7
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Showing 3 changed files with 14 additions and 3 deletions.
diff --git a/qiskit_nature/operators/second_quantization/fermionic_op.py b/qiskit_nature/operators/second_quantization/fermionic_op.py
@@ -205,8 +205,8 @@ def __init__(
             if invalid_labels:
                 raise ValueError(f"Invalid labels for sparse labels are given: {invalid_labels}")
             list_label = [["I"] * self._register_length for _ in labels]
-            prev_index: Optional[int] = None
             for term, label in enumerate(labels):
+                prev_index: Optional[int] = None
                 for split_label in label.split():
                     op_label, index_str = split_label.split("_", 1)
                     index = int(index_str)

diff --git a/releasenotes/notes/bugfix-fermionicop-init-4005d72e38ba67f4.yaml b/releasenotes/notes/bugfix-fermionicop-init-4005d72e38ba67f4.yaml
@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fixed an issue where :class:`~qiskit_nature.operators.FermionicOp` raises
+    unwanted `ValueError` when initialized with some list of sparse label.
diff --git a/test/operators/second_quantization/test_fermionic_op.py b/test/operators/second_quantization/test_fermionic_op.py
@@ -95,8 +95,14 @@ def test_init_invalid_label(self, label, register_length):
 
     def test_init_multiterm(self):
         """Test __init__ with multi terms"""
-        labels = [("N", 2), ("-", 3.14)]
-        self.assertListEqual(FermionicOp(labels).to_list(), labels)
+        with self.subTest("Test 1"):
+            labels = [("N", 2), ("-", 3.14)]
+            self.assertListEqual(FermionicOp(labels).to_list(), labels)
+
+        with self.subTest("Test 2"):
+            labels = [("+-", 1), ("-+", -1)]
+            op = FermionicOp([("+_0 -_1", 1.0), ("-_0 +_1", -1.0)], register_length=2)
+            self.assertListEqual(op.to_list(), labels)
 
     def test_init_multiple_digits(self):
         """Test __init__ for sparse label with multiple digits"""