networkx.algorithms.traversal.depth_first_search.dfs_predecessors¶

dfs_predecessors(G, source=None, depth_limit=None)[source]¶

Returns dictionary of predecessors in depth-first-search from source.

Parameters:	G (NetworkX graph) source (node, optional) – Specify starting node for depth-first search and return edges in the component reachable from source. depth_limit (int, optional (default=len(G))) – Specify the maximum search depth.
Returns:	pred – A dictionary with nodes as keys and predecessor nodes as values.
Return type:	dict

Examples

>>> G = nx.path_graph(4)
>>> nx.dfs_predecessors(G, source=0)
{1: 0, 2: 1, 3: 2}
>>> nx.dfs_predecessors(G, source=0, depth_limit=2)
{1: 0, 2: 1}

Notes

If a source is not specified then a source is chosen arbitrarily and repeatedly until all components in the graph are searched.

The implementation of this function is adapted from David Eppstein’s depth-first search function in PADS, with modifications to allow depth limits based on the Wikipedia article “Depth-limited search”.