Hi JeanPierre,
It's impossible to say much without a reproducible example, including the
graph you used.
My first guess is that your graph contains parallel edges...
Best,
Tiago
Hello Tiago
I appreciate you prompt response.
By construction the graph cannot have parallel edges.
As the graph itself is too big, I have assembled a small sample (grf_sx.txt) which I processed with make_graf.py then paths_from_to() from util.py.
The result is in pathsample.txt
(I have also included lists of vertices and edges with their betweenness and their in- & out- degrees:
I note that the number of edges is 37435 while the input had 39917 entries. I haven't figured out why)
Thanks for your help 
JP
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Hello again Tiago:
I feel foolish. When I looked closely at what I sent you I realised that my initial data had multiple edges from the start. I have to figure this out first before I bother you. So please ignore my previous mail..,
Sorry
JP
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