Copies of vertex_properties aren't really copies
This is probably due to internal stuff of graph-tool, but it doesn't quite behave as I expected. I didn't see a remark in the documentation, it would be nice to have that so others spend less time that I did when searching for bugs. Using the most recent developer version of graph-tool.
$ python
Python 2.7.3 (default, Aug 9 2012, 13:45:17)
[GCC 4.2.1 Compatible Apple Clang 4.0 ((tags/Apple/clang-421.0.60))] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> d1 = {}
>>> d2 = d1
>>> d1
{}
>>> d2
{}
>>> d1[1] = 1
>>> d2[2] = 2
>>> d1
{1: 1, 2: 2}
>>> d2
{1: 1, 2: 2}
>>>
>>> import graph_tool as gt
>>> g = gt.Graph()
>>> vp = g.vertex_properties
>>> g.vertex_properties
{}
>>> vp
{}
>>> g.vertex_properties['prop'] = g.new_vertex_property('bool')
>>> vp['PROP'] = g.new_vertex_property('bool')
>>> g.vertex_properties
{'prop': <PropertyMap object with key type 'Vertex' and value type 'bool', for Graph 0x10f84afd0, at 0x10f8552d0>, 'PROP': <PropertyMap object with key type 'Vertex' and value type 'bool', for Graph 0x10f84afd0, at 0x10f855350>}
>>> vp
{'PROP': <PropertyMap object with key type 'Vertex' and value type 'bool', for Graph 0x10f84afd0, at 0x10f855350>}
>>>