I have a test graph that I would like to filter

import networkx as nx import pickle from pyvis.network import Network central_node='a' nono=['a', 'b', 'c', 'd', 'e', 'f', 'g','h','i','j','k'] eded=[('a', 'b'), ('a', 'c'), ('a', 'd'),('a','f'),('b', 'e'),('c', 'e'),('f', 'd'),('a', 'g'),('e','h'),('e','g'),('i','e'),('j','f'),('k','j')] graph=nx.Graph() graph.add_nodes_from(nono) graph.add_edges_from(eded) net=Network(height='100%', width='100%', bgcolor='white', font_color='black') net.from_nx(graph) net.show('test Graph.html')

Which gives this graph

I am then filtering out all nodes which are further than a radius 2 aroung my central node ‘a’

subgraph=nx.ego_graph(G=graph,n=central_node, radius=2, center=True) subnet.from_nx(subgraph) subnet.show('test SubGraph.html')

which gives this graph (everything ok so far)

Now, the difficult part. I am trying to keep nodes from the subgraph that have at least 3 nodes in common with my central node ‘a’ (in my case the node ‘e’ is the only one I would like to keep).

for node in subgraph.nodes: neighbor = nx.common_neighbors(subgraph,central_node,node) n=len(list(neighbor)) print(node,n) print(list(neighbor)) for i in sorted(neighbor): filtered_nodes.extend(i) if n > 2: neighbors[node]=n filtered_nodes.append(node) filtered_nodes.extend(sorted(neighbor))

And would like to display the resulting graph (displaying nodes a,b,c,e,g and their connecting edges)

But here is the result

filtered_graph=subgraph.subgraph(filtered_nodes) final_net=Network(height='100%', width='100%', bgcolor='white', font_color='black') final_net.from_nx(filtered_graph) final_net.show('Traffic Graph.html')

It seems that the common_neighbors function does return the list of node b,c,g. Whenever I am trying to print it, it displays an empty list. On the other hand, it could count properly the number of common neighbors between node and central node ‘a’.

a 5 [] b 0 [] c 0 [] d 1 [] e 3 [] f 1 [] g 0 [] j 1 []

I cannnot figure out properly which part I am doing wrong.

## Answer

The common_neighbors function doesn’t actually return a list– rather, it returns an iterator, which can be used to generate a list. As a result, when you do `n=len(list(neighbor))`

, you actually consume the iterator, leaving it empty. To fix this, call list on its return value and save that to a variable:

for node in subgraph.nodes: neighbor = list(nx.common_neighbors(subgraph, central_node, node)) n = len(neighbor) print(node, n) print(neighbor) for i in sorted(neighbor): filtered_nodes.extend(i) if n > 2: neighbors[node] = n filtered_nodes.append(node) filtered_nodes.extend(sorted(neighbor))