networkx.algorithms.traversal.breadth_first_search.bfs_predecessors¶
-
bfs_predecessors
(G, source, depth_limit=None, sort_neighbors=None)[source]¶ Returns an iterator of predecessors in breadth-first-search from source.
- Parameters
G (NetworkX graph)
source (node) – Specify starting node for breadth-first search
depth_limit (int, optional(default=len(G))) – Specify the maximum search depth
sort_neighbors (function) – A function that takes the list of neighbors of given node as input, and returns an iterator over these neighbors but with custom ordering.
- Returns
pred – (node, predecessors) iterator where predecessors is the list of predecessors of the node.
- Return type
iterator
Examples
>>> G = nx.path_graph(3) >>> print(dict(nx.bfs_predecessors(G, 0))) {1: 0, 2: 1} >>> H = nx.Graph() >>> H.add_edges_from([(0, 1), (0, 2), (1, 3), (1, 4), (2, 5), (2, 6)]) >>> print(dict(nx.bfs_predecessors(H, 0))) {1: 0, 2: 0, 3: 1, 4: 1, 5: 2, 6: 2} >>> M = nx.Graph() >>> nx.add_path(M, [0, 1, 2, 3, 4, 5, 6]) >>> nx.add_path(M, [2, 7, 8, 9, 10]) >>> print(sorted(nx.bfs_predecessors(M, source=1, depth_limit=3))) [(0, 1), (2, 1), (3, 2), (4, 3), (7, 2), (8, 7)]
Notes
Based on http://www.ics.uci.edu/~eppstein/PADS/BFS.py by D. Eppstein, July 2004. The modifications to allow depth limits based on the Wikipedia article “Depth-limited-search”.
See also
bfs_tree()
,bfs_edges()
,edge_bfs()