Python igraph: get all possible paths in a directed graph

Question

I am using igraph (Python) and would like to get all possible paths between two nodes in a directed graph. I am aware of the function get_all_shortest_paths, wh

Answer 1

Since you mentioned in your question that your ultimate goal is to get only the nodes that are in these paths and not the paths themselves, I think you don't even have to calculate the paths.

The Graph object in igraph has a method called subcomponent. By default, it gives you all the nodes that are in the same (weakly connected) component as a given input node. However, it also has a mode argument. When you set mode to "out", it will give you all the nodes that are reachable from a certain node. When you set mode to "in", it will give you all the nodes from where you can reach a certain node. So, you'll probably need the intersection of the set of reachable nodes from your source vertex and the set of nodes that can reach your target vertex:

s=set(graph.subcomponent(source, mode="out"))
t=set(graph.subcomponent(target, mode="in"))
s.intersection(t)

This is probably way faster than calculating all the paths anyway.