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annotate planemo/lib/python3.7/site-packages/networkx/algorithms/boundary.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 # Copyright (C) 2004-2019 by
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2 # Aric Hagberg <hagberg@lanl.gov>
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3 # Dan Schult <dschult@colgate.edu>
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4 # Pieter Swart <swart@lanl.gov>
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5 # Copyright 2015 NetworkX developers.
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6 # All rights reserved.
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7 # BSD license.
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8 """Routines to find the boundary of a set of nodes.
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9
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10 An edge boundary is a set of edges, each of which has exactly one
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11 endpoint in a given set of nodes (or, in the case of directed graphs,
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12 the set of edges whose source node is in the set).
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13
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14 A node boundary of a set *S* of nodes is the set of (out-)neighbors of
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15 nodes in *S* that are outside *S*.
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16
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17 """
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18 from itertools import chain
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19
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20 __author__ = """Aric Hagberg (hagberg@lanl.gov)\nPieter Swart (swart@lanl.gov)\nDan Schult (dschult@colgate.edu)"""
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21
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22 __all__ = ['edge_boundary', 'node_boundary']
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23
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24
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25 def edge_boundary(G, nbunch1, nbunch2=None, data=False, keys=False,
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26 default=None):
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27 """Returns the edge boundary of `nbunch1`.
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28
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29 The *edge boundary* of a set *S* with respect to a set *T* is the
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30 set of edges (*u*, *v*) such that *u* is in *S* and *v* is in *T*.
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31 If *T* is not specified, it is assumed to be the set of all nodes
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32 not in *S*.
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33
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34 Parameters
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35 ----------
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36 G : NetworkX graph
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37
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38 nbunch1 : iterable
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39 Iterable of nodes in the graph representing the set of nodes
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40 whose edge boundary will be returned. (This is the set *S* from
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41 the definition above.)
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42
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43 nbunch2 : iterable
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44 Iterable of nodes representing the target (or "exterior") set of
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45 nodes. (This is the set *T* from the definition above.) If not
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46 specified, this is assumed to be the set of all nodes in `G`
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47 not in `nbunch1`.
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48
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49 keys : bool
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50 This parameter has the same meaning as in
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51 :meth:`MultiGraph.edges`.
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52
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53 data : bool or object
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54 This parameter has the same meaning as in
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55 :meth:`MultiGraph.edges`.
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56
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57 default : object
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58 This parameter has the same meaning as in
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59 :meth:`MultiGraph.edges`.
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60
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61 Returns
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62 -------
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63 iterator
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64 An iterator over the edges in the boundary of `nbunch1` with
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65 respect to `nbunch2`. If `keys`, `data`, or `default`
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66 are specified and `G` is a multigraph, then edges are returned
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67 with keys and/or data, as in :meth:`MultiGraph.edges`.
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68
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69 Notes
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70 -----
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71 Any element of `nbunch` that is not in the graph `G` will be
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72 ignored.
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73
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74 `nbunch1` and `nbunch2` are usually meant to be disjoint, but in
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75 the interest of speed and generality, that is not required here.
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76
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77 """
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78 nset1 = {v for v in G if v in nbunch1}
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79 # Here we create an iterator over edges incident to nodes in the set
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80 # `nset1`. The `Graph.edges()` method does not provide a guarantee
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81 # on the orientation of the edges, so our algorithm below must
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82 # handle the case in which exactly one orientation, either (u, v) or
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83 # (v, u), appears in this iterable.
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84 if G.is_multigraph():
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85 edges = G.edges(nset1, data=data, keys=keys, default=default)
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86 else:
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87 edges = G.edges(nset1, data=data, default=default)
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88 # If `nbunch2` is not provided, then it is assumed to be the set
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89 # complement of `nbunch1`. For the sake of efficiency, this is
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90 # implemented by using the `not in` operator, instead of by creating
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91 # an additional set and using the `in` operator.
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92 if nbunch2 is None:
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93 return (e for e in edges if (e[0] in nset1) ^ (e[1] in nset1))
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94 nset2 = set(nbunch2)
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95 return (e for e in edges
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96 if (e[0] in nset1 and e[1] in nset2)
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97 or (e[1] in nset1 and e[0] in nset2))
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98
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99
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100 def node_boundary(G, nbunch1, nbunch2=None):
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101 """Returns the node boundary of `nbunch1`.
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102
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103 The *node boundary* of a set *S* with respect to a set *T* is the
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104 set of nodes *v* in *T* such that for some *u* in *S*, there is an
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105 edge joining *u* to *v*. If *T* is not specified, it is assumed to
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106 be the set of all nodes not in *S*.
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107
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108 Parameters
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109 ----------
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110 G : NetworkX graph
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111
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112 nbunch1 : iterable
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113 Iterable of nodes in the graph representing the set of nodes
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114 whose node boundary will be returned. (This is the set *S* from
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115 the definition above.)
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116
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117 nbunch2 : iterable
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118 Iterable of nodes representing the target (or "exterior") set of
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119 nodes. (This is the set *T* from the definition above.) If not
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120 specified, this is assumed to be the set of all nodes in `G`
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121 not in `nbunch1`.
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122
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123 Returns
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124 -------
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125 set
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126 The node boundary of `nbunch1` with respect to `nbunch2`.
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127
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128 Notes
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129 -----
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130 Any element of `nbunch` that is not in the graph `G` will be
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131 ignored.
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132
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133 `nbunch1` and `nbunch2` are usually meant to be disjoint, but in
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134 the interest of speed and generality, that is not required here.
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135
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136 """
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137 nset1 = {n for n in nbunch1 if n in G}
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138 bdy = set(chain.from_iterable(G[v] for v in nset1)) - nset1
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139 # If `nbunch2` is not specified, it is assumed to be the set
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140 # complement of `nbunch1`.
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141 if nbunch2 is not None:
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142 bdy &= set(nbunch2)
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143 return bdy