Python networkx : edge contraction

问题:

I have a NetworkX graph. I would like to know how to do edge contraction between multiple nodes.

For example, if I wanted to contract X, Y and Z:

         _ node A _        _/    |     \_ node X --- node Y --- node Z 

Would become

           node A               |                 node XYZ (or whatever X/Y/Z) 

Graph creation is not the problem. It works. I want to reduce the graph by merging nodes that have the same "meanings": nodes that I call "end lvl" (node name length is equal to 7) and that are linked together.

I have found the condensation function in NetworkX so I tried to use it:

# edge contraction for same nodes # for each node, get the links to other nodes "end lvl" # if there is such a link, it means that these node are # the sames # # copy graph I = G for n,d in G.nodes(data=True):     if n in I.nodes():         if len(n) == 7:             # list of nodes adjacent to n : filter only "end lvl" nodes             neighbors = [ node for node in I.neighbors(n) if len(node) == 7 ]             nodes_to_merges = neighbors.append(n)             I = nx.condensation(I,scc=nodes_to_merges) 

The thing I got when I convert to JSON is:

{"directed": true, "graph": [], "nodes": [{"id": 0}], "links": [], "multigraph": false} 

There is a problem as you can see...

Reference to functions are here.

回答1:

How about:

add_node(XYZ) add_edge(XYZ, A) for edge incident on (X, Y, Z):     v = nodes in edge not in (X, Y, Z, A)     if v:        remove_edge(edge)        add_edge(v, XYZ) for node in (X, Y, Z):     remove_node(node) 

回答2:

Instead of trying to use nx.condensation (which is meant for contracting strongly connected components, not groups of nodes in general) use these functions:

http://networkx.readthedocs.io/en/stable/reference/classes.graph.html#adding-and-removing-nodes-and-edges

to remove all but one of the collapsed nodes and rewire their nodes.

文章来源: Python networkx : edge contraction