markov.py

#!/usr/bin/env python
import random
from pprint import pprint
from collections import defaultdict

def get_words(fname='fyad.txt'):
    with open(fname) as f:
        return f.read().split()

def triplets(words):
    for i in xrange(len(words) - 2):
        yield (words[i], words[i+1], words[i+2])

def chain(words):
    chains = defaultdict(list)
    for w1, w2, w3 in triplets(words):
        pair = (w1, w2)
        chains[pair].append(w3)
    return chains

def markov(chains, words):
    w1, w2 = '\n', '\n'
    output = []
    for word in range(len(words) - 2):
        #first case
        if '\n' in w1 and w2:
            w1, w2 = words[0], words[1]
        w3 = random.choice(chains[(w1, w2)])
        output.append(w3)
        w1, w2 = w2, w3
    return output

if __name__ == '__main__':
    words = get_words('fyad.txt')
    chains = chain(words)
    output = markov(chains, words)
    print ' '.join(output)