Finding cycle of 3 nodes ( or triangles) in a graph

Question

I am working with complex networks. I want to find group of nodes which forms a cycle of 3 nodes (or triangles) in a given graph. As my graph contains about million edges, u

Answer 1

This is a more efficient version of Ajay M answer (I would have commented it, but I've not enough reputation).

Indeed the enumerate_all_cliques method of networkx will return all cliques in the graph, irrespectively of their length; hence looping over it may take a lot of time (especially with very dense graphs).

Moreover, once defined for triangles, it's just a matter of parametrization to generalize the method for every clique length so here's a function:

import networkx as nx

def get_cliques_by_length(G, length_clique):
    """ Return the list of all cliques in an undirected graph G with length 
    equal to length_clique. """
    cliques = []
    for c in nx.enumerate_all_cliques(G) :
        if len(c) <= length_clique:
            if len(c) == length_clique:
                cliques.append(c)            
        else:
            return cliques
    # return empty list if nothing is found
    return cliques

To get triangles just use get_cliques_by_length(G, 3).

Caveat: this method works only for undirected graphs. Algorithm for cliques in directed graphs are not provided in networkx