/usr/lib/python3/dist-packages/networkx/readwrite/graph6.py is in python3-networkx 1.9+dfsg1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 | """Graph6
Read and write graphs in graph6 format.
Format
------
"graph6 and sparse6 are formats for storing undirected graphs in a
compact manner, using only printable ASCII characters. Files in these
formats have text type and contain one line per graph."
See http://cs.anu.edu.au/~bdm/data/formats.txt for details.
"""
# Original author: D. Eppstein, UC Irvine, August 12, 2003.
# The original code at http://www.ics.uci.edu/~eppstein/PADS/ is public domain.
# Copyright (C) 2004-2013 by
# Aric Hagberg <hagberg@lanl.gov>
# Dan Schult <dschult@colgate.edu>
# Pieter Swart <swart@lanl.gov>
# Tomas Gavenciak <gavento@ucw.cz>
# All rights reserved.
# BSD license.
import networkx as nx
from networkx.exception import NetworkXError
from networkx.utils import open_file, not_implemented_for
__author__ = """\n""".join(['Tomas Gavenciak <gavento@ucw.cz>',
'Aric Hagberg <aric.hagberg@lanl.gov'])
__all__ = ['read_graph6', 'parse_graph6', 'generate_graph6', 'write_graph6']
def parse_graph6(string):
"""Read a simple undirected graph in graph6 format from string.
Parameters
----------
string : string
Data in graph6 format
Returns
-------
G : Graph
Raises
------
NetworkXError
If the string is unable to be parsed in graph6 format
Examples
--------
>>> G = nx.parse_graph6('A_')
>>> sorted(G.edges())
[(0, 1)]
See Also
--------
generate_graph6, read_graph6, write_graph6
References
----------
Graph6 specification:
http://cs.anu.edu.au/~bdm/data/formats.txt for details.
"""
def bits():
"""Return sequence of individual bits from 6-bit-per-value
list of data values."""
for d in data:
for i in [5,4,3,2,1,0]:
yield (d>>i)&1
if string.startswith('>>graph6<<'):
string = string[10:]
data = graph6_to_data(string)
n, data = data_to_n(data)
nd = (n*(n-1)//2 + 5) // 6
if len(data) != nd:
raise NetworkXError(\
'Expected %d bits but got %d in graph6' % (n*(n-1)//2, len(data)*6))
G=nx.Graph()
G.add_nodes_from(range(n))
for (i,j),b in zip([(i,j) for j in range(1,n) for i in range(j)], bits()):
if b:
G.add_edge(i,j)
return G
@open_file(0,mode='rt')
def read_graph6(path):
"""Read simple undirected graphs in graph6 format from path.
Parameters
----------
path : file or string
File or filename to write.
Returns
-------
G : Graph or list of Graphs
If the file contains multiple lines then a list of graphs is returned
Raises
------
NetworkXError
If the string is unable to be parsed in graph6 format
Examples
--------
>>> nx.write_graph6(nx.Graph([(0,1)]), 'test.g6')
>>> G = nx.read_graph6('test.g6')
>>> sorted(G.edges())
[(0, 1)]
See Also
--------
generate_graph6, parse_graph6, write_graph6
References
----------
Graph6 specification:
http://cs.anu.edu.au/~bdm/data/formats.txt for details.
"""
glist = []
for line in path:
line = line.strip()
if not len(line):
continue
glist.append(parse_graph6(line))
if len(glist) == 1:
return glist[0]
else:
return glist
@not_implemented_for('directed','multigraph')
def generate_graph6(G, nodes = None, header=True):
"""Generate graph6 format string from a simple undirected graph.
Parameters
----------
G : Graph (undirected)
nodes: list or iterable
Nodes are labeled 0...n-1 in the order provided. If None the ordering
given by G.nodes() is used.
header: bool
If True add '>>graph6<<' string to head of data
Returns
-------
s : string
String in graph6 format
Raises
------
NetworkXError
If the graph is directed or has parallel edges
Examples
--------
>>> G = nx.Graph([(0, 1)])
>>> nx.generate_graph6(G)
'>>graph6<<A_'
See Also
--------
read_graph6, parse_graph6, write_graph6
Notes
-----
The format does not support edge or node labels, parallel edges or
self loops. If self loops are present they are silently ignored.
References
----------
Graph6 specification:
http://cs.anu.edu.au/~bdm/data/formats.txt for details.
"""
if nodes is not None:
ns = list(nodes)
else:
ns = list(G)
def bits():
for (i,j) in [(i,j) for j in range(1,n) for i in range(j)]:
yield G.has_edge(ns[i],ns[j])
n = G.order()
data = n_to_data(n)
d = 0
flush = False
for i, b in zip(range(n * n), bits()):
d |= b << (5 - (i % 6))
flush = True
if i % 6 == 5:
data.append(d)
d = 0
flush = False
if flush:
data.append(d)
string_data = data_to_graph6(data)
if header:
string_data = '>>graph6<<' + string_data
return string_data
@open_file(1, mode='wt')
def write_graph6(G, path, nodes = None, header=True):
"""Write a simple undirected graph to path in graph6 format.
Parameters
----------
G : Graph (undirected)
path : file or string
File or filename to write.
nodes: list or iterable
Nodes are labeled 0...n-1 in the order provided. If None the ordering
given by G.nodes() is used.
header: bool
If True add '>>graph6<<' string to head of data
Raises
------
NetworkXError
If the graph is directed or has parallel edges
Examples
--------
>>> G = nx.Graph([(0, 1)])
>>> nx.write_graph6(G, 'test.g6')
See Also
--------
generate_graph6, parse_graph6, read_graph6
Notes
-----
The format does not support edge or node labels, parallel edges or
self loops. If self loops are present they are silently ignored.
References
----------
Graph6 specification:
http://cs.anu.edu.au/~bdm/data/formats.txt for details.
"""
path.write(generate_graph6(G, nodes=nodes, header=header))
path.write('\n')
# helper functions
def graph6_to_data(string):
"""Convert graph6 character sequence to 6-bit integers."""
v = [ord(c)-63 for c in string]
if len(v) > 0 and (min(v) < 0 or max(v) > 63):
return None
return v
def data_to_graph6(data):
"""Convert 6-bit integer sequence to graph6 character sequence."""
if len(data) > 0 and (min(data) < 0 or max(data) > 63):
raise NetworkXError("graph6 data units must be within 0..63")
return ''.join([chr(d+63) for d in data])
def data_to_n(data):
"""Read initial one-, four- or eight-unit value from graph6
integer sequence.
Return (value, rest of seq.)"""
if data[0] <= 62:
return data[0], data[1:]
if data[1] <= 62:
return (data[1]<<12) + (data[2]<<6) + data[3], data[4:]
return ((data[2]<<30) + (data[3]<<24) + (data[4]<<18) +
(data[5]<<12) + (data[6]<<6) + data[7], data[8:])
def n_to_data(n):
"""Convert an integer to one-, four- or eight-unit graph6 sequence."""
if n < 0:
raise NetworkXError("Numbers in graph6 format must be non-negative.")
if n <= 62:
return [n]
if n <= 258047:
return [63, (n>>12) & 0x3f, (n>>6) & 0x3f, n & 0x3f]
if n <= 68719476735:
return [63, 63,
(n>>30) & 0x3f, (n>>24) & 0x3f, (n>>18) & 0x3f,
(n>>12) & 0x3f, (n>>6) & 0x3f, n & 0x3f]
raise NetworkXError("Numbers above 68719476735 are not supported by graph6")
|