"""
Words/Ladder Graph
------------------
Generate an undirected graph over the 5757 5-letter words in the
datafile words_dat.txt.gz. Two words are connected by an edge
if they differ in one letter, resulting in 14,135 edges. This example
is described in Section 1.1 in Knuth's book [1]_,[2]_.
References
----------
.. [1] Donald E. Knuth,
"The Stanford GraphBase: A Platform for Combinatorial Computing",
ACM Press, New York, 1993.
.. [2] http://www-cs-faculty.stanford.edu/~knuth/sgb.html
"""
__author__ = """\n""".join(['Aric Hagberg (hagberg@lanl.gov)',
'Brendt Wohlberg',
'hughdbrown@yahoo.com'])
# Copyright (C) 2004-2010 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
#-------------------------------------------------------------------
# The Words/Ladder graph of Section 1.1
#-------------------------------------------------------------------
def generate_graph(words):
from string import ascii_lowercase as lowercase
G = nx.Graph(name="words")
lookup = dict((c,lowercase.index(c)) for c in lowercase)
def edit_distance_one(word):
for i in range(len(word)):
left, c, right = word[0:i], word[i], word[i+1:]
j = lookup[c] # lowercase.index(c)
for cc in lowercase[j+1:]:
yield left + cc + right
candgen = ((word, cand) for word in sorted(words)
for cand in edit_distance_one(word) if cand in words)
G.add_nodes_from(words)
for word, cand in candgen:
G.add_edge(word, cand)
return G
def words_graph():
"""Return the words example graph from the Stanford GraphBase"""
import gzip
fh=gzip.open('words_dat.txt.gz','r')
words=set()
for line in fh.readlines():
line = line.decode()
if line.startswith('*'):
continue
w=str(line[0:5])
words.add(w)
return generate_graph(words)
if __name__ == '__main__':
from networkx import *
G=words_graph()
print("Loaded words_dat.txt containing 5757 five-letter English words.")
print("Two words are connected if they differ in one letter.")
print("Graph has %d nodes with %d edges"
%(number_of_nodes(G),number_of_edges(G)))
print("%d connected components" % number_connected_components(G))
for (source,target) in [('chaos','order'),
('nodes','graph'),
('pound','marks')]:
print("Shortest path between %s and %s is"%(source,target))
try:
sp=shortest_path(G, source, target)
for n in sp:
print(n)
except nx.NetworkXNoPath:
print("None")