return an empty generator when there are no edges between source and …

…target
zxcalc · Jul 10, 2024 · 2d82f17 · 2d82f17
1 parent 1e1a5b1
commit 2d82f17
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/pyzx/graph/multigraph.py b/pyzx/graph/multigraph.py
@@ -277,6 +277,9 @@ def edges(self, s=None, t=None):
                         for _ in range(e.w_io): yield (v0, v1, EdgeType.W_IO)
         elif t != None:
             s, t = (s, t) if s < t else (t, s)
+            if t not in self.graph[s]:
+                return
+                yield
             e = self.graph[s][t]
             for _ in range(e.s): yield (s, t, EdgeType.SIMPLE)
             for _ in range(e.h): yield (s, t, EdgeType.HADAMARD)