Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.9/dist-packages/networkx/algorithms/isolate.py: 73%
11 statements
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1"""
2Functions for identifying isolate (degree zero) nodes.
3"""
4import networkx as nx
6__all__ = ["is_isolate", "isolates", "number_of_isolates"]
9@nx._dispatch
10def is_isolate(G, n):
11 """Determines whether a node is an isolate.
13 An *isolate* is a node with no neighbors (that is, with degree
14 zero). For directed graphs, this means no in-neighbors and no
15 out-neighbors.
17 Parameters
18 ----------
19 G : NetworkX graph
21 n : node
22 A node in `G`.
24 Returns
25 -------
26 is_isolate : bool
27 True if and only if `n` has no neighbors.
29 Examples
30 --------
31 >>> G = nx.Graph()
32 >>> G.add_edge(1, 2)
33 >>> G.add_node(3)
34 >>> nx.is_isolate(G, 2)
35 False
36 >>> nx.is_isolate(G, 3)
37 True
38 """
39 return G.degree(n) == 0
42@nx._dispatch
43def isolates(G):
44 """Iterator over isolates in the graph.
46 An *isolate* is a node with no neighbors (that is, with degree
47 zero). For directed graphs, this means no in-neighbors and no
48 out-neighbors.
50 Parameters
51 ----------
52 G : NetworkX graph
54 Returns
55 -------
56 iterator
57 An iterator over the isolates of `G`.
59 Examples
60 --------
61 To get a list of all isolates of a graph, use the :class:`list`
62 constructor::
64 >>> G = nx.Graph()
65 >>> G.add_edge(1, 2)
66 >>> G.add_node(3)
67 >>> list(nx.isolates(G))
68 [3]
70 To remove all isolates in the graph, first create a list of the
71 isolates, then use :meth:`Graph.remove_nodes_from`::
73 >>> G.remove_nodes_from(list(nx.isolates(G)))
74 >>> list(G)
75 [1, 2]
77 For digraphs, isolates have zero in-degree and zero out_degre::
79 >>> G = nx.DiGraph([(0, 1), (1, 2)])
80 >>> G.add_node(3)
81 >>> list(nx.isolates(G))
82 [3]
84 """
85 return (n for n, d in G.degree() if d == 0)
88@nx._dispatch
89def number_of_isolates(G):
90 """Returns the number of isolates in the graph.
92 An *isolate* is a node with no neighbors (that is, with degree
93 zero). For directed graphs, this means no in-neighbors and no
94 out-neighbors.
96 Parameters
97 ----------
98 G : NetworkX graph
100 Returns
101 -------
102 int
103 The number of degree zero nodes in the graph `G`.
105 """
106 # TODO This can be parallelized.
107 return sum(1 for v in isolates(G))