"""This module contains a code example related to
Think Python, 2nd Edition
by Allen Downey
http://thinkpython2.com
Copyright 2015 Allen Downey
License: http://creativecommons.org/licenses/by/4.0/
"""
from __future__ import print_function, division
import anagram_sets
def metathesis_pairs(d):
"""Print all pairs of words that differ by swapping two letters.
d: map from word to list of anagrams
"""
for anagrams in d.values():
for word1 in anagrams:
for word2 in anagrams:
if word1 < word2 and word_distance(word1, word2) == 2:
print(word1, word2)
def word_distance(word1, word2):
"""Computes the number of differences between two words.
word1, word2: strings
Returns: integer
"""
assert len(word1) == len(word2)
count = 0
for c1, c2 in zip(word1, word2):
if c1 != c2:
count += 1
return count
if __name__ == '__main__':
sets = anagram_sets.all_anagrams('words.txt')
metathesis_pairs(sets)
