dfs_predecessors

dfs_predecessors(G, source=None, depth_limit=None, *, sort_neighbors=None)

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

Parameters:

GNetworkX graph

sourcenode, optional

Specify starting node for depth-first search. Note that you will get predecessors for all nodes in the component containing source. This input only specifies where the DFS starts.

depth_limitint, optional (default=len(G))

Specify the maximum search depth.

sort_neighborsfunction (default=None)

A function that takes an iterator over nodes as the input, and returns an iterable of the same nodes with a custom ordering. For example, sorted will sort the nodes in increasing order.

Returns:

pred: dict

A dictionary with nodes as keys and predecessor nodes as values.

See also

dfs_preorder_nodes

dfs_postorder_nodes

dfs_labeled_edges

edge_dfs()

bfs_tree()

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”.

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}