Parse state-to-state difference moments in addition to transition moments

Update StateToStateParser regex to match both "transition moments" and
"difference moments" sections (e.g., <2|W|2> difference density).

Fix SimpleLineParser first_only option to work without a title by checking
if any of the output keys already exist before updating.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: smparker

mudslide/turboparse/line_parser.py

@@ -50,6 +50,9 @@ def process(self, m, out):
                 if not (self.first_only and self.title in out):
                     out[self.title] = data
             else:
+                # For first_only without title, check if any of the keys already exist
+                if self.first_only and any(n in out for n in self.names):
+                    return
                 out.update(data)
         else:
             if self.title not in out:

mudslide/turboparse/response_parser.py

@@ -85,8 +85,8 @@ class StateToStateParser(ParseSection):
 
     def __init__(self):
         super(self.__class__,
-              self).__init__(r"<\s*\d+\s*\|\s*W\s*\|\s*\d+\s*>\s*transition moments",
-                             r"(<\s*\d+\s*\|\s*W\s*\|\s*\d+\s*>\s*transition moments)|(S\+T\+V CONTRIBUTIONS TO)",
+              self).__init__(r"<\s*\d+\s*\|\s*W\s*\|\s*\d+\s*>.*(?:transition|difference) moments",
+                             r"(<\s*\d+\s*\|\s*W\s*\|\s*\d+\s*>.*(?:transition|difference) moments)|(S\+T\+V CONTRIBUTIONS TO)",
                              multi=True)
 
 

test/test_turboparse.py

@@ -241,13 +241,21 @@ def test_state_to_state_parsed(self, parsed):
         """Test that state-to-state transition moments are parsed"""
         assert 'state-to-state' in parsed['egrad']
         s2s = parsed['egrad']['state-to-state']
-        # Only <1|W|2> is parsed (labeled as "transition moments")
-        # <2|W|2> is labeled as "difference moments" and not captured
-        assert len(s2s) == 1
+        # Should have 2 blocks: <2|W|2> difference moments and <1|W|2> transition moments
+        assert len(s2s) == 2
+
+    def test_state_to_state_2_2(self, parsed):
+        """Test <2|W|2> difference moments"""
+        s2s = parsed['egrad']['state-to-state'][0]
+        assert s2s['bra'] == 2
+        assert s2s['ket'] == 2
+        # Relaxed electric transition dipole moment (length rep.) from line 549
+        # z = 3.819847
+        assert np.isclose(s2s['diplen']['z'], 3.819847)
 
     def test_state_to_state_1_2(self, parsed):
         """Test <1|W|2> transition moments"""
-        s2s = parsed['egrad']['state-to-state'][0]
+        s2s = parsed['egrad']['state-to-state'][1]
         assert s2s['bra'] == 1
         assert s2s['ket'] == 2
         # Relaxed electric transition dipole moment (length rep.) from line 608