Hi,
I'm using python-igraph (0.7.1) and when I save a graph with an integer attribute as GraphML, attr.type= "double" is used instead of "int". See a minimal example below.
Regards,
In [1]: import igraph as ig
In [2]: g = ig.Graph()
In [3]: g.add_vertex()
In [4]: g.vs["size"] = [1]
In [5]: g.vs[0]
Out[5]: igraph.Vertex(<igraph.Graph object at 0x7f25969f0430>,0,{'size': 1})
In [6]: g.write_graphml("test.graphml")
In [7]: %cat test.graphml
<?xml version="1.0" encoding="UTF-8"?>
<!-- Created by igraph -->
<key id="v_size" for=""
attr.name="size" attr.type="double"/>
<graph id="G" edgedefault="undirected">
<node id="n0">
<data key="v_size">1</data>
</node>
</graph>
</graphml>
--