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edge_dfs(G, source=None, orientation=None)

Yield the edges of G in a depth-first-search order continuing until all edges are generated.

Notes

The goal of this function is to visit edges. It differs from the more familiar depth-first traversal of nodes, as provided by ~networkx.algorithms.traversal.depth_first_search.dfs_edges , in that it does not stop once every node has been visited. In a directed graph with edges [(0, 1), (1, 2), (2, 1)], the edge (2, 1) would not be visited if not for the functionality provided by this function.

Parameters

G : graph: A directed/undirected graph/multigraph.
source : node, list of nodes: The node from which the traversal begins. If None, then a source is chosen arbitrarily and repeatedly until all edges from each node in the graph are searched.
orientation : None | 'original' | 'reverse' | 'ignore' (default: None): For directed graphs and directed multigraphs, edge traversals need not respect the original orientation of the edges. When set to 'reverse' every edge is traversed in the reverse direction. When set to 'ignore', every edge is treated as undirected. When set to 'original', every edge is treated as directed. In all three cases, the yielded edge tuples add a last entry to indicate the direction in which that edge was traversed. If orientation is None, the yielded edge has no direction indicated. The direction is respected, but not reported.

A directed, depth-first-search of edges in G, beginning at :None:None:`source`.

Yields

edge : directed edge: A directed edge indicating the path taken by the depth-first traversal. For graphs, :None:None:`edge` is of the form :None:None:`(u, v)` where u and :None:None:`v` are the tail and head of the edge as determined by the traversal. For multigraphs, :None:None:`edge` is of the form :None:None:`(u, v, key)`, where :None:None:`key` is the key of the edge. When the graph is directed, then u and :None:None:`v` are always in the order of the actual directed edge. If orientation is not None then the edge tuple is extended to include the direction of traversal ('forward' or 'reverse') on that edge.

Examples

>>> nodes = [0, 1, 2, 3]
... edges = [(0, 1), (1, 0), (1, 0), (2, 1), (3, 1)]

>>> list(nx.edge_dfs(nx.Graph(edges), nodes))
[(0, 1), (1, 2), (1, 3)]

>>> list(nx.edge_dfs(nx.DiGraph(edges), nodes))
[(0, 1), (1, 0), (2, 1), (3, 1)]

>>> list(nx.edge_dfs(nx.MultiGraph(edges), nodes))
[(0, 1, 0), (1, 0, 1), (0, 1, 2), (1, 2, 0), (1, 3, 0)]

>>> list(nx.edge_dfs(nx.MultiDiGraph(edges), nodes))
[(0, 1, 0), (1, 0, 0), (1, 0, 1), (2, 1, 0), (3, 1, 0)]

>>> list(nx.edge_dfs(nx.DiGraph(edges), nodes, orientation="ignore"))
[(0, 1, 'forward'), (1, 0, 'forward'), (2, 1, 'reverse'), (3, 1, 'reverse')]

>>> list(nx.edge_dfs(nx.MultiDiGraph(edges), nodes, orientation="ignore"))
[(0, 1, 0, 'forward'), (1, 0, 0, 'forward'), (1, 0, 1, 'reverse'), (2, 1, 0, 'reverse'), (3, 1, 0, 'reverse')]

See :

Back References

The following pages refer to to this document either explicitly or contain code examples using this.

networkx.algorithms.traversal.edgedfs.edge_dfs networkx.algorithms.traversal.depth_first_search.dfs_edges networkx.algorithms.traversal.depth_first_search.dfs_tree networkx.algorithms.traversal.depth_first_search.dfs_successors networkx.algorithms.traversal.depth_first_search.dfs_predecessors networkx.algorithms.traversal.edgebfs.edge_bfs networkx.algorithms.traversal.depth_first_search.dfs_postorder_nodes

Local connectivity graph

Hover to see nodes names; edges to Self not shown, Caped at 50 nodes.

Using a canvas is more power efficient and can get hundred of nodes ; but does not allow hyperlinks; , arrows or text (beyond on hover)

SVG is more flexible but power hungry; and does not scale well to 50 + nodes.

All aboves nodes referred to, (or are referred from) current nodes; Edges from Self to other have been omitted (or all nodes would be connected to the central node "self" which is not useful). Nodes are colored by the library they belong to, and scaled with the number of references pointing them