# encoding: utf-8
"""
Functions for identifying isolate (degree zero) nodes.
"""
# Copyright (C) 2004-2015 by
# Aric Hagberg <hagberg@lanl.gov>
# Dan Schult <dschult@colgate.edu>
# Pieter Swart <swart@lanl.gov>
# All rights reserved.
# BSD license.
import networkx as nx
__author__ = """\n""".join(['Drew Conway <drew.conway@nyu.edu>',
'Aric Hagberg <hagberg@lanl.gov>'])
__all__=['is_isolate','isolates']
[docs]def is_isolate(G,n):
"""Determine of node n is an isolate (degree zero).
Parameters
----------
G : graph
A networkx graph
n : node
A node in G
Returns
-------
isolate : bool
True if n has no neighbors, False otherwise.
Examples
--------
>>> G=nx.Graph()
>>> G.add_edge(1,2)
>>> G.add_node(3)
>>> nx.is_isolate(G,2)
False
>>> nx.is_isolate(G,3)
True
"""
return G.degree(n)==0
[docs]def isolates(G):
"""Return list of isolates in the graph.
Isolates are nodes with no neighbors (degree zero).
Parameters
----------
G : graph
A networkx graph
Returns
-------
isolates : list
List of isolate nodes.
Examples
--------
>>> G = nx.Graph()
>>> G.add_edge(1,2)
>>> G.add_node(3)
>>> nx.isolates(G)
[3]
To remove all isolates in the graph use
>>> G.remove_nodes_from(nx.isolates(G))
>>> G.nodes()
[1, 2]
For digraphs isolates have zero in-degree and zero out_degre
>>> G = nx.DiGraph([(0,1),(1,2)])
>>> G.add_node(3)
>>> nx.isolates(G)
[3]
"""
return [n for (n,d) in G.degree_iter() if d==0]