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annotate planemo/lib/python3.7/site-packages/networkx/algorithms/isolate.py @ 1:56ad4e20f292 draft

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"planemo upload commit 6eee67778febed82ddd413c3ca40b3183a3898f1"
author guerler
date Fri, 31 Jul 2020 00:32:28 -0400
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1 # -*- encoding: utf-8 -*-
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2 # Copyright 2015 NetworkX developers.
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3 # Copyright (C) 2004-2019 by
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4 # Aric Hagberg <hagberg@lanl.gov>
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5 # Dan Schult <dschult@colgate.edu>
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6 # Pieter Swart <swart@lanl.gov>
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7 # All rights reserved.
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8 # BSD license.
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9 """
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10 Functions for identifying isolate (degree zero) nodes.
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11 """
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12 import networkx as nx
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13
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14 __author__ = """\n""".join(['Drew Conway <drew.conway@nyu.edu>',
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15 'Aric Hagberg <hagberg@lanl.gov>'])
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16
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17 __all__ = ['is_isolate', 'isolates', 'number_of_isolates']
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18
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19
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20 def is_isolate(G, n):
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21 """Determines whether a node is an isolate.
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22
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23 An *isolate* is a node with no neighbors (that is, with degree
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24 zero). For directed graphs, this means no in-neighbors and no
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25 out-neighbors.
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26
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27 Parameters
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28 ----------
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29 G : NetworkX graph
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30
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31 n : node
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32 A node in `G`.
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33
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34 Returns
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35 -------
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36 is_isolate : bool
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37 True if and only if `n` has no neighbors.
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38
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39 Examples
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40 --------
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41 >>> G=nx.Graph()
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42 >>> G.add_edge(1,2)
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43 >>> G.add_node(3)
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44 >>> nx.is_isolate(G,2)
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45 False
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46 >>> nx.is_isolate(G,3)
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47 True
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48 """
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49 return G.degree(n) == 0
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50
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51
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52 def isolates(G):
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53 """Iterator over isolates in the graph.
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54
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55 An *isolate* is a node with no neighbors (that is, with degree
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56 zero). For directed graphs, this means no in-neighbors and no
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57 out-neighbors.
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58
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59 Parameters
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60 ----------
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61 G : NetworkX graph
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62
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63 Returns
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64 -------
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65 iterator
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66 An iterator over the isolates of `G`.
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67
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68 Examples
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69 --------
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70 To get a list of all isolates of a graph, use the :class:`list`
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71 constructor::
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72
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73 >>> G = nx.Graph()
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74 >>> G.add_edge(1, 2)
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75 >>> G.add_node(3)
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76 >>> list(nx.isolates(G))
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77 [3]
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78
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79 To remove all isolates in the graph, first create a list of the
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80 isolates, then use :meth:`Graph.remove_nodes_from`::
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81
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82 >>> G.remove_nodes_from(list(nx.isolates(G)))
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83 >>> list(G)
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84 [1, 2]
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85
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86 For digraphs, isolates have zero in-degree and zero out_degre::
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87
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88 >>> G = nx.DiGraph([(0, 1), (1, 2)])
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89 >>> G.add_node(3)
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90 >>> list(nx.isolates(G))
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91 [3]
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92
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93 """
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94 return (n for n, d in G.degree() if d == 0)
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95
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96
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97 def number_of_isolates(G):
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98 """Returns the number of isolates in the graph.
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99
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100 An *isolate* is a node with no neighbors (that is, with degree
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101 zero). For directed graphs, this means no in-neighbors and no
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102 out-neighbors.
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103
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104 Parameters
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105 ----------
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106 G : NetworkX graph
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107
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108 Returns
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109 -------
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110 int
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111 The number of degree zero nodes in the graph `G`.
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112
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113 """
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114 # TODO This can be parallelized.
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115 return sum(1 for v in isolates(G))