Hello, I remember an old discussion about vectors of floats saved using the C99 hexadecimal notation. However, a colleague found out that also a simple float property map is saved using that notation and this is giving him troubles of interoperability. As an example from graph_tool.all import * g = Graph() n = g.add_vertex() n1 = g.add_vertex() e = g.add_edge(n,n1) p = g.new_edge_property('float') p[e]=3.14 g.edge_properties['weight']=p g.save('float-test.xml') float-test.xml then contains: ... <key id="key0" for="edge" attr.name="weight" attr.type="float" /> ... <edge id="e0" source="n0" target="n1"> <data key="key0">0x1.91eb851eb851fp+1</data> </edge> Is this the expected behaviour? Also, there is no difference if we change the type from float to double. Thanks, Giuseppe