## Mercurial > repos > shellac > sam_consensus_v3

### view env/lib/python3.9/site-packages/networkx/algorithms/wiener.py @ 0:4f3585e2f14b draft default tip

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"planemo upload commit 60cee0fc7c0cda8592644e1aad72851dec82c959"

author | shellac |
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date | Mon, 22 Mar 2021 18:12:50 +0000 |

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"""Functions related to the Wiener index of a graph.""" from itertools import chain from .components import is_connected from .components import is_strongly_connected from .shortest_paths import shortest_path_length as spl __all__ = ["wiener_index"] #: Rename the :func:`chain.from_iterable` function for the sake of #: brevity. chaini = chain.from_iterable def wiener_index(G, weight=None): """Returns the Wiener index of the given graph. The *Wiener index* of a graph is the sum of the shortest-path distances between each pair of reachable nodes. For pairs of nodes in undirected graphs, only one orientation of the pair is counted. Parameters ---------- G : NetworkX graph weight : object The edge attribute to use as distance when computing shortest-path distances. This is passed directly to the :func:`networkx.shortest_path_length` function. Returns ------- float The Wiener index of the graph `G`. Raises ------ NetworkXError If the graph `G` is not connected. Notes ----- If a pair of nodes is not reachable, the distance is assumed to be infinity. This means that for graphs that are not strongly-connected, this function returns ``inf``. The Wiener index is not usually defined for directed graphs, however this function uses the natural generalization of the Wiener index to directed graphs. Examples -------- The Wiener index of the (unweighted) complete graph on *n* nodes equals the number of pairs of the *n* nodes, since each pair of nodes is at distance one:: >>> n = 10 >>> G = nx.complete_graph(n) >>> nx.wiener_index(G) == n * (n - 1) / 2 True Graphs that are not strongly-connected have infinite Wiener index:: >>> G = nx.empty_graph(2) >>> nx.wiener_index(G) inf """ is_directed = G.is_directed() if (is_directed and not is_strongly_connected(G)) or ( not is_directed and not is_connected(G) ): return float("inf") total = sum(chaini(p.values() for v, p in spl(G, weight=weight))) # Need to account for double counting pairs of nodes in undirected graphs. return total if is_directed else total / 2