fix: fixed graph-tool import for vector-valued vertex properties, closes

 #741

CHANGELOG.md

@@ -1,5 +1,12 @@
 # igraph Python interface changelog
 
+## [main]
+
+### Fixed
+
+- Fixed import of `graph-tool` graphs for vertex properties where each property
+  has a vector value.
+
 ## [0.11.3] - 2023-11-19
 
 ### Added

src/igraph/io/libraries.py

@@ -248,9 +248,12 @@ def _construct_graph_from_graph_tool(cls, g):
 
     # Node attributes
     for key, val in g.vertex_properties.items():
+        # val.get_array() returns None for non-scalar types so use the slower
+        # way if this happens
         prop = val.get_array()
+        arr = prop if prop is not None else val
         for i in range(vcount):
-            graph.vs[i][key] = prop[i]
+            graph.vs[i][key] = arr[i]
 
     # Edges and edge attributes
     # NOTE: graph-tool is quite strongly typed, so each property is always