/usr/lib/python3/dist-packages/networkx/algorithms/components/semiconnected.py is in python3-networkx 1.11-1ubuntu2.
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"""
Semiconnectedness.
"""
__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']
@not_implemented_for('undirected')
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:]))
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