This documents an unmaintained version of NetworkX. Please upgrade to a maintained version and see the current NetworkX documentation.

Source code for networkx.algorithms.components.semiconnected

# -*- coding: utf-8 -*-

__author__ = """ysitu <ysitu@users.noreply.github.com>"""
# Copyright (C) 2014 ysitu <ysitu@users.noreply.github.com>
# All rights reserved.
# BSD license.

import networkx as nx
from networkx.utils import not_implemented_for

__all__ = ['is_semiconnected']

[docs]def is_semiconnected(G): """Return True if the graph is semiconnected, False otherwise. A graph is semiconnected if, and only if, for any pair of nodes, either one is reachable from the other, or they are mutually reachable. Parameters ---------- G : NetworkX graph A directed graph. Returns ------- semiconnected : bool True if the graph is semiconnected, False otherwise. Raises ------ NetworkXNotImplemented : If the input graph is not directed. NetworkXPointlessConcept : If the graph is empty. Examples -------- >>> G=nx.path_graph(4,create_using=nx.DiGraph()) >>> print(nx.is_semiconnected(G)) True >>> G=nx.DiGraph([(1, 2), (3, 2)]) >>> print(nx.is_semiconnected(G)) False See Also -------- is_strongly_connected, is_weakly_connected """ if len(G) == 0: raise nx.NetworkXPointlessConcept( 'Connectivity is undefined for the null graph.') if not nx.is_weakly_connected(G): return False G = nx.condensation(G) path = nx.topological_sort(G) return all(G.has_edge(u, v) for u, v in zip(path[:-1], path[1:]))