markov.py

#!/usr/bin/env python
"""
markov chain string generator thing

"""
from collections import defaultdict
import itertools
import random
import sys

# constant
sentinel = '\n'

def file_to_list(fname):
    with open(fname) as f:
        output =  ' '.join(line.strip() for line in f)
    return output.split()

# add sentinel value
words = file_to_list(fname) + list(sentinel)

def triplets(words):
    # yield triplets until sentinel is reached
    for idx, word in enumerate(words):
        if sentinel in (words[idx], words[idx+1]):
            break
        else:
            yield ((words[idx], words[idx + 1]), words[idx + 2])

triplets = triplets(words)

def make_chains(triplets):
    chains = defaultdict(list)
    for prefix, suffix in triplets:
        chains[prefix].append(suffix)
    return chains 

chains = make_chains(triplets)

def generate(words, chains, prefix, max_length=10000):
    # yield a word until the sentinel value is reached.
    while True:
        if sentinel in prefix:
            break
        else:
            word = random.choice(chains[prefix])
            yield word
            prefix = (prefix[1], word)

if __name__ == '__main__':
    prefix = tuple(words[:2])
    output = [elem for elem in itertools.chain(sentinel, prefix)]
    for word in generate(words, chains, prefix):
        output.append(word)
    print ' '.join(output)