iterating over nodes of a NetworkX DiGraph in-order

Question

Is there a way to iterate over the nodes of a NetworkX DiGraph in order? The traversal methods I found iterate over edges rather than nodes, or require a source. In my case, my DAG has multiple sources. I don't really care in which order these sources are iterated over, as long as one node does not get processed before all of its ancestors have been processed.

Answer 1

I usually implement something like this:

import networkx as nx

G = nx.gnr_graph(100, 0.1)

root_node = list(G.nodes)[80]

children_next = set()
searched_nodes = set()
children_current = [root_node]

level = 0
while len(children_current) != 0:


    for n in children_current:
        searched_nodes.add(n)

        for s in G.successors(n): #exchange with predecessors to get parents
            children_next.add(s)

        children_next = children_next.difference(searched_nodes)

    children_current = list(children_next)

    level += 1

    print("root={}; level={}, successors={}".format(root_node, level, str(children_current)))

This allows me to travers the graph in a direction (exchange G.successors(n) with G.predecessors(n) to change the direction). It traverses the nodes of the graph according to their distance from the root node.